Rev. C 24-Aug-01

Features

3 identical bidirectional link channels allowing full duplex communication under
selectable transmit rate from 1.25 up to 200 Mbit/s in each direction

A COmmunication Memory Interface (COMI) provides autonomous accesses to a
communication memory which are controlled by an arbitration unit, allowing two
TSS901E to share one Dual Port Ram without external arbitration

The scalable databus width (8/16/32 bit) allows flexible integration with any CPU type

Little or big endian mode is configurable

AHOst Control Interface (HOCI) gives read/write accesses to the TSS901E
configuration registers and to the DS-link channels for the controlling CPU

Device control via one of the three links allows its use in systems without a local
controller

Link disconnect detection and parity check at token (data and control) level; possible
checksum generation for packet level check

Power saving mode relying on automatic transmit rate reduction

Auser's manual of the TSS901E (also called SMCS332) is available at:
http://www.omimo.be/companies/dasa_000.htm

Designed on Atmel MG1140E matrix and packaged into MQFPL196

Description and Applications

The TSS901E provides an interface between a Data-Strobe link - according to the
IEEE Std 1355-1995 specification carrying a simple interprocessor communication
protocol - and a data processing node consisting of a CPU and a communication and
data memory.

The TSS901E offers hardware supported execution of the major parts of the interpro-
cessor communication protocol: data transfer between two nodes of a multi-processor
system is performed with minimal host CPU intervention. The TSS901E can execute
simple commands to provide basic features for system control functions; a provision of
fault tolerant features exists as well.

Although the TSS901E initial exploitation is for use in multi-processor systems where
the high speed links standardisation is an important issue and where reliability is a
requirement, it could be used in applications such as heterogeneous systems or mod-
ules without any communication feature like special image compression chips, some
signal processors, application specific programmable logic or mass memory.

The TSS901E may also be used in single board systems where standardised high
speed interfaces are needed and systems containing "non-intelligent" modules such
as A/D-converter or sensor interfaces which can be assembled with the TSS901E
thanks to the "control by link" feature.

Tripple Point to
Point IEEE 1355
High Speed
Controller

TSS901E

TSS901E

Rev. C 24-Aug-01

Introduction

The TSS901E provides an interface between a Data-Strobe link according to the IEEE
Std 1355-1995 specification carrying the simple interprocessor communication proto-
col

(1)

and a data processing node consisting of a CPU and communication and data

memory. The TSS901E provides HW supported execution of the major parts of the sim-
ple interprocessor communication protocol, particularly:

transfer of data between two modes of a multi-processor system with minimal host
CPU intervention,

execution of simple commands to provide basic features for system control
functions,

provision of fault tolerant features.

However, with disabling of features such as the protocol handling or with reduction of
the transmit rate (TSS901E automatically reduces transmit rate for sending null tokens)
also low power usage is supported.

Figure 1. TSS901E Block Diagram

Target applications are heterogeneous multi-processor systems supported by scalable
interfaces including the little/big endian swapping. The TSS901E connects modules with
different processors (e.g. TSC21020F, ERC32, TSC695E and others). Any kind of net-
work topology could be realized through the high speed point-to-point IEEE1355-links
(see chapter Applications).

Rastetter P. et.al., Simple Interprocessor Communication Protocol Specification, DIP-
SAPII-DAS-31-01, Issue 3, 08.10.96, also available on the same web site as the users
guide.

Receive

Transmit

macro

cell

Channel 2

RX1_DS

TX1_DS

RX2_DS

TX2_DS

Channel 1

JTAG

COMI

HOCI

PRCI

Test

CADR

CCTRL

CDATA

HADR

HCTRL

HDATA

HINT

RCPU

SES

UTIL

Protocol

Channel 3

RX3_DS

TX3_DS

TSS901E

Rev. C 24-Aug-01

Interfaces

The TSS901E consists of the following blocks (See Figure 1):

bidirectional link channels, all comprising the DS-link macro cell (DSM), receive
and transmit sections (each including FIFOs) and a protocol processing unit (PPU).
Each channel allows full duplex communication up to 200 Mbit/s in each direction.
With protocol command execution a higher level of communication is supported.
Link disconnect detection and parity check at token level are performed. A
checksum generation for a check at packet level can be enabled.

The transmit rate is selectable between 1.25 and 200 Mbit/s; an additional power
saving mode can be enabled, where the transmit rate is automatically reduced to 10
Mbit/s when only Null tokens are being transmitted over the link. The default trans-
mit rate is 10 Mbit/s. For special applications the data transmit rate can be
programmed to values even below 10 Mbit/s; the lowest possible (to be within the
IEEE-1355 specification) transmit rate is 1.25 Mbit/s (the next values are 2.5 and 5
Mbit/s).

Communication Memory Interface (COMI) performs autonomous accesses to the
communication memory of the module to store data received via the links or to read
data to be transmitted via the links. The COMI consists of individual memory
address generators for the receive and transmit direction of every DS link channel.
The access to the memory is controlled via an arbitration unit providing a fair
arbitration scheme. Two TSS901E can share one DPRAM without external
arbitration.

The data bus width is scalable (8/16/32 bit) to allow flexible integration with any
CPU type.

Operation in little or big endian mode is configurable through internal registers.
The COMI address bus is 16 bit wide allowing direct access of up to 64K words of
the DPRAM. Two chip select signals are provided to allow splitting of the 64k
address space in two memory banks.

Host Control Interface (HOCI) gives read and write access to the TSS901E
configuration registers and to the DS-link channels for the controlling CPU. Viewed
from the CPU, the interface behaves like a peripheral that generates acknowledges
to synchronize the data transfers and which is located somewhere in the CPU's
address space.

Packets can be transmitted or received directly via the HOCI. In this case the Com-
munication Memory (DPRAM) is not strictly needed. However, in this case the
packet size should be limited to avoid frequent CPU interaction.

The data bus width is scalable (8/16/32 bit) to allow flexible integration with any
CPU type. The byte alignment can be configured for little or big endian mode
through an external pin.

Additionally the HOCI contains the interrupt signalling capability of the TSS901E by
providing an interrupt output, the interrupt status register and interrupt mask register
to the local CPU.

A special pin is provided to select between control of the TSS901E by HOCI or by
link. If control by link is enabled, the host data bus functions as a 32-bit general pur-
pose interface (GPIO).

Protocol Command Interface (PRCI) that collects the decoded commands from all
PPUs and forwards them to external circuitry via 5 special pins.

JTAG Test Interface that represents the boundary scan testing provisions specified
by IEEE Standard 1149.1 of the Joint Testing Action Group (JTAG). The TSS901E'
test access port and on-chip circuitry is fully compliant with the IEEE 1149.1
specification. The test access port enables boundary scan testing of circuitry
connected to the TSS901E I/O pins.

TSS901E

Rev. C 24-Aug-01

Operation Modes

According to the different protocol formats expected for the operation of the TSS901E,
two major operation modes are implemented into the TSS901E. The operation modes
are chosen individually for each link channel by setting the respective configuration reg-
isters via the HOCI or via the link.

Transparent Mode (default after reset): This mode allows complete transparent
data transfer between two nodes without performing any interpretation of the
databytes and without generating any acknowledges. It is completely up to the host
CPU to interpret the received data and to generate acknowledges if required.

The TSS901E accepts EOP1 and EOP2 control tokens as packet delimiters and
generates autonomously EOP1/EOP2 (as configured) markers after each end of a
transmission packet.

This mode also includes as a special submode:

Wormhole routing: This mode allows hardware routing of packets by the
TSS901E.

Simple Interprocessor Communication (SIC) Protocol Mode: This mode executes
the simple interprocessor communication protocol as described in the protocol
specification

(1)

. The following capabilities of the protocol are implemented into the

TSS901E:

interpretation of the first 4 data tokens as the header bytes of the protocol

autonomous execution of the simple control commands as described in the
protocol specification

(1)

autonomous acknowledgement of received packets if configured

In transmit direction no interpretation of the data is performed. This means that for
transmit packets, the four header bytes must be generated by the host CPU and
must be available as the first data read from the communication memory.
EOP1/EOP2 control tokens are automatically inserted by the TSS901E when one
configured transfer from the communication memory has finished.

Rastetter P. et.al., Simple Interprocessor Communication Protocol Specification, DIP-
SAPII-DAS-31-01, Issue 3, 08.10.96, also available on the same web site as the users
guide.

TSS901E

Rev. C 24-Aug-01

TSS901E Control by Link

A feature of the TSS901E is the possibility to control the TSS901E not only via HOCI but
via one of the three links. This allows to use the TSS901E in systems without a local
controller (µController, FPGA etc.). Since the HOCI is no longer used in this operation
mode, it is instead available as a set of general purpose I/O (GPIO) lines.

Wormhole Routing

The TSS901E introduces a wormhole routing function similar to the routing implemented
in the ST-Microelectronics C104 routing switch. Each of the three links and the
TSS901E itself can be assigned an eight bit address. When routing is enabled in the
TSS901E, the first byte of a packet will be interpreted as the address destination byte,
analysed and removed from the packet (header deletion). If this address matches one of
the two other link addresses or the TSS901E address assigned previously, the packet
will be automatically forwarded to this link or the FIFO of the TSS901E. If the header
byte does not match a link address, the packet will be written to the internal FIFO as well
and an error interrupt (maskable) will be raised.

PPU Functional
Description

Since the Protocol Processing Unit (PPU) determines a major part of the TSS901E func-
tionality, the principal blocks of the PPU and their function are described here. This
functionality is provided for every DS link channel of the TSS901E.

Protocol Execution Unit: This unit serves as the main controller of the PPU block.
It receives the tokens from the DS macrocell and interprets (in protocol mode) the
four header data characters received after an EOP1/EOP2 control character. If the
address field matches the link channel address and the command field contains a
valid command then forwarding of data into the receive FIFO is enabled. If the
command field contains a "simple control command" then the execution request is
forwarded to the command execution unit.

The protocol execution unit also enables forwarding of header data characters to
the acknowledge generator and provides an error signal in case of address mis-
match, wrong commands or disabled safety critical "simple control commands".

The protocol execution unit is disabled in "transparent" or "wormhole routing" opera-
tion mode.

Receive, Transmit, Acknowledge: The transmit and receive FIFOs decouple the
DS link related operations from the TSS901E related operations in all modes and
such allows to keep the speed of the different units even when the source or sink of
data is temporarily blocked.

In the protocol mode a further FIFO (acknowledge FIFO) is used to decouple send-
ing of acknowledges from receiving new data when the transmit path is currently
occupied by a running packet transmission.

Command Execution Unit: This unit performs activating resp. deactivating of the
CPU reset and the specific external signals and provides the capability to reset one
or all links inside the TSS901E, all actions requested by the decoded commands
from the protocol execution unit.

The unit contains a register controlling the enable/disable state of safety critical
commands which is set into the 'enable' state upon command request and which is
reset after a safety critical command has been executed.

The CPU reset and the specific external signals are forwarded to the Protocol Com-
mand Interface (PRCI).

Part Number TSS901E

Document Outline