eroflex Circuit T

echnology

 Data Bus Modules For The Future SCDCT1999 REV B 8/14/01

Features

· Performs the Complete Dual-Redundant Remote Terminal and Bus Controller Protocol

Functions of MIL-STD-1553B

· Automatic Switchover to Superseding Input Commands
· MIL-PRF-38534 Compliant Circuits Available
· 750 mw Typical Power Consumption
· Small Size
· Available in Plug-in or Flatpack Configuration
· Compatible with all ACT Driver/Receiver Units
· 5V DC Operation
· Direct replacement for CT1602
· Full Military (-55°C to +125°C) Temperature Range

General Description

The CT1999 design incorporates ASIC and five Octal Buffers that accomplish the dual redundant
MIL-STD1553B Remote Terminal and/or Bus Controller Protocol Functions. Buffering has been added to the
most commonly used output signals on the CT1999, minimizing external hardware requirements. The CT1999
connects directly to all ACT Driver/Receiver Units.

Encoder

Decoder

"O"

Decoder

"1"

Driver

Select

Enable

BUS "0"

BUS "1"

T/R

Hybrid

T/R

Hybrid

Internal

Highway

Control

Discrete

Output
Buffers

Internal

Highway

Buffer

SA & WC

Buffers

Interface

Unit

Control

Data I/O

Sub Address

Word Count

Outputs

Buffered

Descrete

Outputs

Unbuffered

Outputs

Control

Inputs

Terminal

Address

Inputs

Block Diagram (With Transformer)

ASIC

CT1999

Remote Terminal and/or Bus Controller

CT1999

for MIL-STD-1553B

CIRCUIT TECHNOLOGY

www.aeroflex.com

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

Absolute Maximum Ratings

Parameter

Range

Units

Operating Free-air Temperature

-55°C to +125

°C

Storage Case Temperature

-65°C to +150

°C

Power Supply Voltage V

Volts

Input Voltage

Volts

Recommended Operating Conditions

Parameter

Min

Typ

Max

Unit

Power Supply Voltage V

4.5

5.0

5.5

High Level Input Voltage, Vcc = 5V

2.2

Low Level Input Voltage, Vcc = 5V

0.7

Electrical Characteristics

= -55

°C to +125°C)

Parameter

Test Conditions

Min

Max

Unit

Notes

High Level Output Voltage

= -3mA

= -400µA

= -800µA

= 4.5V

2.4

2B,5

Low Level Output Voltage

= +12mA

= +4mA

= +2mA

= 4.5V

0.4

2B,5

High Level Input Current

= 5.5V, V

= 2.4V

-700

-20

-700

-400

-200

-25

µA

2A,2B

Low Level Input Current

= 5.5V, V

= 0.4V

-900

-200

-900

-500

-350

-25

µA

2A,2B

Supply Current

= 5.5V

285

Notes (Pin numbers are for 90 pin Plug in package):

1. Pins 45 through 50 (RTADPAR,RTAD0,1,2,3,4). 2A. Pin 34 (IHDIR). 2B. Pins 37 through 44 (IH08 through
IH715). 3. Pins 24,36 (BUFINH, IHENA). 4. ALL remaining inputs ALL versions. 5. Pins 2 through 23 (Remaining
Buffered Outputs). 6. Pins 68,69,70,71 (TXINH0,TXINH1,TXDATA,TXDATA). 7. All remaining outputs.

Clock Requirements

Frequency

Stability (-55°C to +125°C)

Maximum Asymmetry

Rise/Fall Time

6MHz

±0.01%

48 - 52%

10ns MAX

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

REMOTE TERMINAL OPERATION

Receive Data Operation

All valid data words associated with a valid receive data command word for the RT are passed to the subsystem. The
RT examines all command words from the bus and will respond to valid (i.e. correct Manchester, parity coding etc.)
commands which have the correct RT address (or broadcast address if the RT broadcast option is enabled). When the
data words are received, they are decoded and checked by the RT and, if valid, passed to the subsystem on a word by
word basis at 20 µs intervals. This applies to receive data words in both Bus Controller to RT and RT to RT messages.
When the RT detects that the message has finished, it checks that the correct number of words have been received
and if the message is fully valid, then a Good Block Received signal is sent to the subsystem, which must be used by
the subsystem as permission to use the data just received.

The subsystem must therefore have a temporary buffer store up to 32 words long into which these data words can be
placed. The Good Block Received signal will allow use of the buffer store data once the message has been validated.

If a block of data is not validated, then Good Block Received will not be generated. This may be caused by any sort of
message error or by a new valid command for the RT being received on another bus to which the RT must switch.

Transmit Data Operation

If the RT receives a valid transmit data command addressed to the RT, then the RT will request the data words from the
subsystem for transmission on a word by word basis. To allow maximum time for the subsystem to collect each data
word, the next word is requested by the RT as soon as the transmission of the current word has commenced.

It is essential that the subsystem should provide all the data words requested by the RT once a transmit sequence has
been accepted. Failure to do so will be classed by the RT as a subsystem failure and reported as such to the Bus
Controller.

Control of Data Transfers

This section describes the detailed operation of the data transfer mechanism between RT and subsystems. It covers
the operations of the signals DTRQ, DTAK, IUSTB, H/L, GBR, NBGT, TX/RX during receive data and transmit data
transfers.

Figure 7 shows the operation of the data handshaking signals during a receive command with two data words. When
the RT has fully checked the command word, NBGT is pulsed low, which can be used by the subsystem as an
initialization signal. TX/RX will be set low indicating a receive command. When the first data word has been fully
validated, DTRQ is set low. The subsystem must then reply within approximately 1.5 µs by setting DTAK low. This
indicates to the RT that the subsystem is ready to accept data The data word is then passed to the subsystem on the
internal highway IH08-IH715 in two bytes using IUSTB as a strobe signal and H/L as the byte indicator (high byte first
followed by low byte). Data is valid about both edges of IUSTB. Signal timing for this handshaking is shown in Figure
12.

If the subsystem does not declare itself busy, then it must respond to DTRQ going low by setting DTAK low within
approximately 1.5 us. Failure to do so will be classed by the RT as a subsystem failure and reported as such to the Bus
Controller.

It should be noted that IUSTB is also used for internal working in the RT. DTRQ being low should be used as an enable
for clocking data to the subsystem with IUSTB.

Once the receive data block has finished and been checked by the RT, GBR is pulsed low if the block is entirely correct
and valid. This is used by the subsystem as permission to make use of the data block If no GBR signal is generated,
then an error has been detected by the RT and the entire data block is invalid and no data words in it may be used.

If the RT is receiving data in an RT to RT transfer, the data handshaking signals will operate in an identical fashion but
there will be a delay of approx 70 µs between NBGT going low and DTRQ first going low. See Figure 10.

Figure 6 shows the operation of the data handshaking signals during transmit command with three, data words. As with
the receive command discussed previously, NBGT is pulsed low if the command is valid and for the RT. TX/RX will be
set high indicating a transmit data command. While the RT is transmitting its status word, it requests the first data word
from the subsystem by setting DTRQ low. The subsystem must then reply within approximately 13.5 µs by setting
DTAK low. By setting DTAK low, the subsystem is indicating that it has the data word ready to pass to the RT. Once
DTAK is set low by the subsystem, DTRQ should be used together with H/L and TX/RX to enable first the high byte and
then the low byte of the data word onto the internal highway IH08-IH715. The RT will latch the data bytes during IUSTB,
and will then return DTRQ high. Data for each byte must remain stable until IUSTB has returned low. Signal timing for
this handshaking is shown in Figure 11.

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

Additional Data Information Signals

At the same time as data transfers take place, a number of information signals are made available to the subsystem.
These are INCMD, the subaddress lines SA0-4, the word count lines WC0-4 and current word count lines CWC0-4.
Use of these signals is optional.

INCMD will go active low while the RT is servicing a valid command for the RT. The subaddress, transmit/receive bit.
and word count from the command word are all ma a vailable to the subsystem as SA0-4, TX/RX and WC0-4
respectively. They may be sampled when INCMD goes low and will remain valid while INCMD is low.

The subaddress is intended to be used by the subsystem as an address pointer for the data block Subaddress 0 and
31 are mode commands, and there can be no receive or transmit data blocks associated with these. (Any data word
associated with a mode command uses different handshaking operations. If the subsystem does not use all the
subaddresses available, then some of the subaddress lines may be ignored.

The TX/RX signal indicates the direction of data transfer across the RT - subsystem interface. Its use is described in
the previous section.

The word count tells the subsystem the number of words to expect to receive or transmit in a message, up to 32 words.
A word count of all 0s indicates a count of 32 words.

The current word count is set to 0 at the beginning of a new message and is incremented following each data word
transfer across the RT - subsystem interface. (It is clocked on the falling edge of the second IUSTB pulse in each word
transfer). It should be noted that there is no need for the subsystem to compare the word count and current word count
to validate the number of words in a message. This is done by the RT.

Subsystem Use of Status Bits and Mode Commands

General Description

Use of the status bits and the mode commands is one of the most confusing aspects of MIL-STD-1553B. This is
because much of their use is optional, and also because some involve only the RT while others involve both the RT and
the subsystem.

The CT1999 allows full use to be made of all the status bits, and also implements all the mode commands. The
subsystem is given the opportunity to make use of status bits, and is only involved in mode commands which have a
direct impact on the subsystem.

The mode commands in which the subsystem may be involved are Synchronize, Sychronize with data word, Transmit
Vector Word, Reset and Dynamic Bus Control Allocation. The status bits to which the subsystem has access are
Service Request, Busy, Subsystem Flag and Dynamic Bus Control Acceptance. Operation of each of these mode
commands and of the status bits is described in the following sections.

The subsystem designer should note that all other mode commands and status bits are serviced internally by the RT,
and the subsystem has no access to them. In particular, the terminal flag and message error status bits and BIT word
contents are all controlled internally by the RT.

Synchronize Mode Commands

Once the RT has validated the command word and checked for the correct address, the SYNC line is set low. The
signal WC4 will be set low for a Synchronize mode command Figure 16, and high for a Synchronize with data word
mode command Figure 15. In a Synchronize with data word mode command, SYNC remains low during the time that
the data word is received. Once the data word has been validated, it is passed to the subsystem on the internal
highway IH08-IH715 in two bytes using IUSTB as a strobe signal and H/L as the byte indicator (high byte first followed
by low byte). SYNC being low should be used on the enable to allow IUSTB to clock synchronize mode data to the
subsystem.

If the subsystem does not need to implement either of these mode commands, the SYNC signal can be ignored, since
the RT requires no response from the subsystem.

Transmit Vector Word Mode Command

Figure 14 illustrates the relevant signal timings for an RT receiving a valid Transmit Vector Word mode command. The
RT requests data by setting VECTEN low. The subsystem should use H/L to enable first the high byte and then the low
byte of the Vector word onto the internal highway IH08-IH715.

It should be noted that the RT expects the Vector word contents to be already prepared in a latch ready for enabling
onto the internal highway when VECTEN goes low. If the subsystem has not been designed to handle the Vector word

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

mode command, it will be the fault of the Bus Controller if the RT receives such a command. Since the subsystem is
not required to acknowledge the mode command, the RT will not be affected in any way by Vector word circuitry not
being implemented in the subsystem. It will however transmit a data word as the Vector word, but this word will have
no meaning.

Reset Mode Command

Figure 8 shows the relevant signal timings for an RT receiving a valid reset mode command. Once the command
word has been fully validated and serviced, the RESET signal is pulsed low. This signal may be used as a reset
function for subsystem interface circuitry.

Dynamic Bus Allocation

This mode command is intended for use with a terminal which has the capability of configuring itself into a bus
controller on command from the bus. The line DBCREQ cannot go true unless the DBCACC line was true at the time
of the valid command, i.e. tied low. For terminals acting only as RTs, the signal DBCACC should be tied high
(inactive), and the signal DBCREQ should be ignored and left unconnected.

Use of the Busy Status Bit

The Busy Bit is used by the subsystem to indicate that it is not ready to handle data transfers either to or from the RT.

The RT sets the bit to logic one if the BUSY line from the subsystem is active low at the time of the second falling
edge of INCLK after INCMD goes low. This is shown in Figure 13. Once the Busy bit is set, the RT will stop all receive
and transmit data word transfers to and from the subsystem. The data transfers in the Synchronize with data word
and Transmit Vector word mode commands are not affected by the Busy bit and will take place even if it has been set.

It should be noted that a minimum of 0.5 µs subaddress decoding time is given to the subsystem before sending of
status bits. This allows the subsystem to selectively set the Busy bit if for instance one subaddress is busy but others
are ready. This option will prove useful when an RT is interfacing with multiple subsystems.

Use of the Service Request Status Bit

The Service Request bit is used by the subsystem to indicate to the Bus Controller that an asynchronous service is
requested.

The timing of the setting of this bit is the same as the Busy bit and is shown in Figure 13. Use of SERVREQ has no
effect on the RT apart from sening the Service Request bit.

It should be noted that certain mode commands require that the last status word be transmitted by the RT instead of
the current one, and therefore a currently set status bit will not be seen by the Bus Controller. Therefore the user is
advised to hold SERVREQ low until the requested service takes place.

Use of the Subsystem Status Bit

This status bit is used by the RT to indicate a subsystem fault condition. If the subsystem sets SSERR low at any
time, the subsystem fault condition in the RT will be set, and the Subsystem Flag status bit will subsequently be set
The fault condition will also be set if a handshaking failure takes place during a data transfer to or from the
subsystem. The fault condition is cleared on power-up or by a Reset mode command.

Dynamic Bus Control Acceptance Status Bit

DBCACC, when set true, enables an RT to configure itself into a Bus Controller, if the subsystem has the capability,
by allowing DBCREQ to pulse true and BIT TIME 18 to be set in the status response. If Dynamic Bus Control is not
required then DBCACC must be tied high. DBCACC tied high inhibits DBCREQ and clears BIT TIME 18 in the status
response.

Bus Driver/Receiver Interface

Receive Data

The decoder chip requires two TTL signals (PDIN & NDIN) to represent the data coming in from the bus. PDIN should
be driven to a logic level `1' when the bus waveform exceeds a specified positive threshold and NDIN should be
driven to a logic level `1' when a specified negative threshold is exceeded. During the quiet period on the bus both
signals should be at the same logic level. All the bus receivers must be permanently enabled, the selection if the bus
in use is done within the ASIC.

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

Transmit Data

The signals generated by the encoder chip (PDOUT & NDOUT) are of the same format as the receive data The only
difference is that the TTL signals are negative logic, e.g. the signal is active when on logic level "0". This means that
when the encoder is quiet both PDOUT & NDOUT are at logic level `1'. Both the signals should be used in conjunction
with TXEN and the appropriate driver enable, e.g. (CS0 - enable for bus 0). TXEN only enables the driver when it
should be transmitting, and the driver enable routes the data on to the bus in use.

Figure 5 shows an example of a typical interface circuit between the CT1999 and a driver/receiver unit.

BUS CONTROL OPERATION

To enable its use in a bus controller each chip in the chipset has additional logic within it. This logic can be enabled by
pulling the pin labelled RT/BC low. Once the chipset is in bus control mode, all data transfers must be initiated by the
bus control processor correctly commanding the chipset via the subsystem interface. In bus control mode six inputs are
activated which in RT mode are inoperative and four signals with dual functions exercise the second function (the first
being for the RT operation).

To use the CT1999 as a 1553B bus control interface, the bus control processor must be able to carry out four basic
bus-related functions. Two inputs, BCOPA and BCOPB allow these four options to be selected. The option is then
initiated by sending a negative-going strobe on the BCOPSTB input. BCOPSTB must only be strobed low when NDRQ
is high. This is particularly important when two options are required during a single transfer.

With these options all message types and lengths can be handled. Normal BC/RT exchanges are carried out in the
chipset option zero. This is selected by setting BCOPA and BCOPB to a zero and strobing BCOPSTB. On receipt of the
strobe, the CT1999 loads the command word from an external latch using CWEN and H/L The command word is
transmitted down the bus. The TX/RX bit is, however, considered by the chipset as being its inverse and so if a transmit
command is sent to a RT, Figure 17, the chipset in BC mode believes it has been given a receive command. As the RT
returns the requested number of data words plus its status, the BC chipset carries out a full validation check and
passes the data into the subsystem using DTRQ, DTAK, H/L, IUSTB and CWC as in RT operation. It also supplies
GBR at the end of a valid transmission. Conversely, a receive command sent down the bus is interpreted by the BC
chipset as a transmit command, and so the requisite data words are added to the command word, see Figure 18.

For mode commands, where a single command word is required, option one is selected by strobing BCOPSTB when
BCOPA is high and BCOPB is low. On receiving the strobe, the command word is loaded from the external latch using
CWEN and H/L, the correct sync and parity bits are added and the word transmitted, see Figure 20. Mode commands
followed by a data word requires option two. Option two, selected by strobing BCOPSTB while BCOPA is low and
BCOPB is high, loads a data word via DWEN and H/L, adds sync and parity and transmits them to the bus, see Figure
21. If the mode code transmitted required the RT to return a data word, then selecting option three by strobing
BCOPSTB when BCOPA and BCOPB are both high will identify that data word and if validated, output it to the
subsystem interface using RMDSTB and H/L This allows data words resulting from mode codes to be identified
differently from ordinary data words and routed accordingly, see Figure 22. All received status words are output to the
subsystem interface using STATSTB and H/L.

In BC option three, if the signal PASMON is active, then all data appearing on the selected bus is output to the
subsystem using STATSTB for command and status words or RMDSTB for data words.

RT to RT transfers require the transmission of two command words. A receive command to one RT is contiguously
followed by a transmit command to the the other RT. This can be achieved by selecting option one followed by option
zero for the second command. The strobe (BCOPSTB) for option zero must be delayed until NDRQ has gone low and
returned high following the strobe for option one. The RT transmissions are checked and transferred in the subsystem
interface to the bus control processor, see Figure 19.

Note: For all BC operations, BCOPA and BCOPB must remain valid and stable for a minimum of 1 µs following the
leading (negative going) edge of BCOPSTB.

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

Pin Description

Signal

Hybrid

Sink or Source

Signal Description

RX DATA 0/1

SINK

Positive Date In. This should be a TTL description of the positive, half of the
Manchester code data on the bus. It should be driven to a logic level "1" when
a predetermined positive threshold is exceeded on the bus.

RX DATA 0/1

SINK

Negative Data In. This should be a TTL description of the negative half of the
Manchester code data on the bus. It should be driven to a logic level "1" when
a predetermined negative threshold is exceeded on the bus.

TX INHIBIT 0/1

SOURCE

Transmitter Enable. Goes low when the transmitter is transmitting. Should be
used to enable the bus drivers.

TX DATA

SOURCE

Positive Data Out - When this signal goes high the bus should be driven
positive.

TX DATA

SOURCE

Negative Data Out - When this signal goes high the bus should be driven
negative.

RTAD 0-4

SINK

RT address lines - These should be hardwired by the user. RTAD4 is the most
significant bit.

RTADPAR

SINK

RT address parity line - This must be hardwired by the user to give odd parity.

BCSTEN 0/1

SINK

Recognition of Broadcast command enable - When low the recognition of
broadcast command is prevented on the specified bus.

6MCK

SINK

6 Megahertz master clock.

IH 08
IH 19
IH 210
IH 311
IH 412
IH 513
IH614
IH715

SINK/SOURCE

Internal Highway - Bi-directional 8 bit highway on which 16 bit words are
passed in two bytes. IH 715 is the most significant bit of each byte, the most
significant byte being transferred first. The highway should only be driven by
the subsystem when data is to be transferred to the RT.

DTRQ

SOURCE

Data Transfer Request - Goes low to request a data transfer between the
ASIC and subsystem. Goes high at the end of the transfer.

DTAK

SINK

Data Transfer Acknowledge - Goes low to indicate that the subsystem is
ready for the data transfer.

IUSTB

SOURCE

Interface Unit Strobe - This is a double pulse strobe used to transfer the two
bytes of data

H/L

SOURCE

High/Low - Indicates which byte of data is on the internal highway. Logic level
"0" for least significant byte.

GBR

SOURCE

Good Block Received - Pulses low for 500ns when a block of data has been
received by the ASIC and has passed all the validity and error checks.

NBGT

SOURCE

New Bus Grant - Pulses low whenever a new command is accepted by the
ASIC.

TX/RX

SOURCE

Transmit/Receive - The state of this line informs the subsystem whether it is
to transmit or receive data The signal is valid while INCMD is low.

INCMD

SOURCE

In Command - Goes low when the RT is servicing a valid command. The
subaddress and word count lines are valid while the signal is low.

WC 0-4

SOURCE

Word Count - These five lines specify the requested number of data words to
be received or transmitted. Valid when INCMD is low.

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

SA 0-4

SOURCE

Sub Address - These five lines are a label for the data being transferred. Valid
when INCMD is low.

CWC 0-4

SOURCE

Current Word Count - These five lines define which data word in the message
is currently being transferred.

SYNC

SOURCE

Synchronize - Goes low when a synchronize mode code is being serviced.

VECTEN/DWEN

SOURCE

Vector Word Enable/DataWord Enable - In the RT mode, this signal is
provided to enable the contents of the vector word latch (which is situated in
the subsystem) onto the ASIC's internal highway. This signal, when in the Bus
Controller mode, is used to enable mode code data from the subsystem onto
the internal highway.

RESET

SOURCE

Reset - This line pulses low for 500ns on completion of the servicing of a valid
and legal mode command to reset remote terminal.

SSERR

SINK

Subsystem Error - By taking this line low, the subsystem can set the
Subsystem Flag in the Status Word.

BUSY

SINK

Busy - This signal should be driven low if the subsystem is not ready to
perform a data transfer to or from the ASIC.

SERVREQ

SINK

Service Request - This signal should be driven low to request an
asynchronous transfer and left low until the transfer has taken place.

INCLK

SOURCE

Internal Clock (2 MHz) - This is made available for synchronization use by the
subsystem if required. However, many of the outputs to the subsystem are
asynchronous.

EOT

SOURCE

End of Transmission - Goes low if a valid sync plus two data bits do not
appear in time to be contiguous with preceding word.

RTADER

SOURCE

Remote Terminal Address Error - This line goes low if an error is detected in
the RT address parity of the selected receiver. Any receiver detecting an error
in the RT address will turn itself off.

HSFAIL

SOURCE

Handshake Failure - This line pulses low if the allowable time for DTAK
response has been exceeded during the ASIC/subsystem data transfer
handshaking.

LSTCMD/CWEN

SOURCE

Last Command/Command Word Enable - This line pulses low when
servicing a valid and legal mode command to transmit last command. When in
RT mode this line must not be used to enable data from the subsystem. This
line also pulses low, when in the Bus Control mode, when a command word is
required for transmission.

STATEN/
STATSTB

SOURCE

Status Enable/Status Strobe - This line pulses low to enable the status word
onto the internal highway for transmission. When in RT mode this line must not
be used to enable data from the subsystem. This line also pulses high, when in
the Bus Control mode, to strobe received status words into the subsystem.
When PASMON is true this line pulses high for Command and Status words.

BITEN/
RMDSTB

SOURCE

Built In Test Enable/Receive Mode Data Strobe - This line pulses low when
servicing a valid and legal mode command to transmit the internal BIT word.
This signal is for information only and must not be used to enable data from the
subsystem. This line also pulses high when in the Bus Control mode when
mode data is received to be passed to the subsystem and when data is passed
to the subsystem during PASMON.

DWSYNC

SOURCE

Data Word Sync - This line goes low if a data word sync and two Manchester
biphase bits are valid.

Pin Description (Cont.)

Signal

Hybrid

Sink or Source

Signal Description

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

CMSYNC

SOURCE

Command Word Sync - This line goes low if a command word sync and two
Manchester biphase bits are valid.

NDRQ

SOURCE

No Data Required - This line goes low if the encoder transmit buffer is full i.e.
another word is going to be transmitted. This signal is for information only and
must not be used to enable data from the subsystem.

PASMON

SINK

Passive Monitor - When functioning as a Bus Controller this line acts as a
passive monitor select. The active going edge of this line will cause the
REQBUS lines to be latched and that bus, now selected will be monitored so
long as PASMON remains low. All traffic on the bus will be handed, after
validation, to the subsystem via STATSTB for status and commands words,
and RMDSTB for data words.

BCOPSTB

SINK

Bus Controller Operation Strobe - When functioning as a Bus Controller a
low going pulse on this line will initiate the selected bus controller operation on
the requested bus, using BCOPA&B and REQBUSA&B.

BCOPA

SINK

Bus Control Operation A - Least significant bit of the bus controller operation
select lines.

BCOPB

SINK

Bus Control Operation B - Most significant bit of the bus controller operation
select lines.

REQBUS A

SINK/SOURCE

Request Bus A - This line,wwhen in RT mode, is the least significant bit of the
bus request lines which specify the origin of the command, ie. they are
sources. When in BC mode these lines are sinks and specify which bus is to be
used for the next command.

REQBUS B

SINK/SOURCE

Request Bus B - Most significant bit of the bus request lines. (See above for
description.)

RT/BC

SINK

Remote Terminal/Bus Control - This line when high causes the ASIC to
function as a remote terminal. When low the ASIC functions as a bus controller
or passive monitor.

DBCACC

SINK

Dynamic Bus Control Accept - This line should be permanently tied low if a
subsystem is able to accept control of the bus if offered.

LTFAIL

SOURCE

Loop Test Fail - This line goes low if any error in the transmitted waveform is
detected or if any parity error in the hardwired RT address is detected.

ERROR

SOURCE

Error - This line latches low if a Manchester or parity error is detected. It is
reset by the next CMSYNC (RT mode) and also by RTO in the BC mode.

RTO

SOURCE

Reply Time Out - This signal will pulse low whenever the reply time for a
transmitting terminal has been exceeded. This line is intended for the bus
controller use.

TXTO

SOURCE

Transmitter Time Out - This line goes true if the transmitter time out limits are
exceeded.

PARER

SOURCE

Parity Error - This line will pulse low if a parity error is detected by the
decoder.

MANER

SOURCE

Manchester Error - This line will pulse low if a Manchester error is detected by
the decoder.

DBCREQ

SOURCE

Dynamic Bus Control Request - This line will pulse low when the status reply
for a mode code Dynamic Bus Control has finished where the accept bit was
set.

VALD

SOURCE

Valid Data - This line will pulse low when a valid data word is received.

Pin Description (Cont.)

Signal

Hybrid

Sink or Source

Signal Description

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

BUF INH

SINK

Buffer Inhibit - A low on this line causes the Buffered Signals to assume a
high impedance state.

IH ENA

SINK

Internal Highway Enable - A low on this line enables the Internal Highway
transceiver to transmit or receive data which is controlled by the IH DIR Line.

IH DIR

SINK

Internal Highway Direction - Controls the direction of data through the
Internal Highway Transceiver.
High = To Subsystem
Low = From Subsystem

RX DATA 0/1

SINK

RX DATA 0/1

SINK

TX INHIBIT 0/1

SOURCE

Transmitter Enable. Goes low when the transmitter is transmitting. Should be
used to enable the bus drivers.

TX DATA

SOURCE

Positive Data Out - When this signal goes high the bus should be driven
positive.

Pin Description (Cont.)

Signal

Hybrid

Sink or Source

Signal Description

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

T/R

Bit

Mode Code

Function

Associated

Data Word

Broadcast Command

Allowed

00000

Dynamic Bus Control

00001

Synchronize

Yes

00010

Transmit Status Word

00011

Initiate Self Test

Yes

00100

Transmitter Shutdown

Yes

00101

Override Transmitter Shutdown

Yes

00110

Inhibit Terminal Flag Bit

Yes

00111

Override lnhibit Terminal Flag Bit

Yes

01000

Reset Remote Terminal

Yes

01001

Reserved

TBD

01111

Reserved

TBD

10000

Transmit Vector Word

Yes

10001

Synchronize

Yes

10010

Transmit Last Command

Yes

10011

TransmitBlTWord

Yes

10100

Selected Transmitter Shutdown

Yes

10101

Override Selected Transmitter

Shutdown

Yes

1 or 0

10110

Reserved

Yes

TBD

1 or 0

11111

Reserved

Yes

TBD

Figure 2 Assigned Mode Codes

Controller to
RT Transfer

Receive

Command

Data

Word

Data

Word

. . . .

Data

Word

. .

Status

Word

Command

Word

RT to
Controller
Transfer

Transmit

Command

. .

Status

Word

Data

Word

Data

Word

. . . .

Data

Word

Command

Word

RT to RT
Transfer

Receive

Command

Transmit

Command

. .

Status

Word

Data

Word

Data

Word

. . . .

Data

Word

. .

Status

Word

Command

Word

Mode Command

Without Data
Word

Mode

Command

. .

Status

Word

Command

Word

Mode Command

With Data
Word
(Transmit)

Mode

Command

. .

Status

Word

Data

Word

Command

Word

Mode Command

With Data
Word
(Receive)

Mode

Command

Data

Word

. .

Status

Word

Command

Word

NOTE: § = Intermessage Gap

. .

= Response Time

Figure 1 Typical Message Formats

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

BIT TIMES

COMMAND
WORD

SYNC

REMOTE TERMINAL

ADDRESS

T/R

SUBADDRESS/MODE

DATA WORD

COUNT/MODE CODE

DATA WORD

DATA

LSB 20

BIT WORD

SYNC

STATUS WORD

SYNC

REMOTE TERMINAL

ADDRESS

RESERVED

Note: T/R Transmit/Receive

P Parity

r
ans

i
t
t
er T

i
m

eou

t
on B

r
ans

i
t
t
er T

i
m

eou

t
on B

r
ans

i
t
t
er T

i
m

eou

t
on B

r
ans

i
t
t
er T

i
m

eou

t
on B

3 S

down

2 S

down

1 S

down

0 S

down

r
oadc

t
T

r
ans

i
t

Dat

Rec

i
v

rd Count

I
l
l
ega

l
M

ode

Com

and

ode T

/
R

i
t
Wrong

op T

t

F

i
l
u

ubsyst

Handshak

e F

i
l
u

r
a

i
t
t
e

r T

i
m

eout

l
ag

ge E

rror

I
n

t
r
u

ent

i
o

r
v

i
c

e Reque

r
o

adc

t
Com

i
v

t
em

l
ag

nam

i
c

Cont

rol

ept

anc

r
m

i
nal

l
ag

r
i
t
y

Figure 3 Word Count

Aeroflex Circuit Technology

SCDCT1999 REV B 8/14/01 Plainview NY (516) 694-6700

Pin Out Description

Pin #

Function

Pin #

Pin

# FP

Function

Pin #

Pin

# FP

Function

REQBUSB

ERROR

CWC 00 (LSB)

REQBUSA

LTFAIL

SA 04 (MSB)

COMMON & CASE

MANER

SA 03

IH DIR

PARER

SA 02

VALD

CWC 04 (MSB)

IH ENA

RTADER

CWC 03

IH 00/08 (LSB)

RX DATA 01

CWC 02

IH 01/09

RX DATA 01

CWC 01

IH 02/10

+5 VIN

GBR

IH 03/11

TX INHIBIT 01

H/L

IH 04/12

TX INHIBIT 00

STATEN/STATSTB

IH 05/13

TX DATA

EOT

IH 06/14

TX DATA

SA 01

IH 07/15 (MSB)

SERVREQ

SA 00 (LSB)

TXTO

INCMD

DBCACC

TX/RX

RTADPAR

RESET

DTRQ

RTAD 00 (LSB)

RT/BC

VECTEN/DWEN

RTAD 01

DBCREQ

NBGT

RTAD 02

HSFAIL

SYNC

RTAD 03

LSTCMD/CWEN

INCLK

RTAD 04 (MSB)

BITEN/RMDSTB

IUSTB

CMSYNC

BUSY

24 24

BUF

INH

DWSYNC

WC 04 (MSB)

DTAK

BCSTEN 00

WC 03

BCOPA

RX DATA 0

WC 00 (LSB)

BCOPSTB

RX DATA 0

SSERR

BCOPB

BCSTEN 01

WC 02

PASMON

RTO

WC 01

NDRQ

6 MCK

Part Number CT1999