Features
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3 identical bidirectional link channels allowing full duplex communication under
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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
A user’s manual of the TSS901E (also called SMCS332) is available at:
http://www.spacewire.esa.int/tech/spacewire/products/index.htm
Designed on Atmel MG1140E matrix and packaged into MQFPL196
Triple Point to
Point IEEE 1355
High Speed
Controller
TSS901E
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.
4167F–AERO–06/07
Introduction
The TSS901E provides an interface between a Data-Strobe link according to the IEEE Std
1355-1995 specification carrying the simple interprocessor communication protocol
(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 simple interprocessor communication
protocol, particularly:
•
•
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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 trans-
mit rate (TSS901E automatically reduces transmit rate for sending null tokens) also low power
usage is supported.
Figure 1.
TSS901E Block Diagram
Receive
COMI
RX1_DS
TX1_DS
DS
macro
cell
CADR
CCTRL
CDATA
Protocol
HADR
HCTRL
Transmit
HOCI
Channel 1
HINT
HDATA
RX2_DS
TX2_DS
Channel 2
PRCI
RCPU
SES
UTIL
RX3_DS
TX3_DS
Channel 3
Test
JTAG
Target applications are heterogeneous multi-processor systems supported by scalable inter-
faces including the little/big endian swapping. The TSS901E connects modules with different
processors (e.g. TSC21020F, ERC32, TSC695E and others). Any kind of network topology
could be realized through the high speed point-to-point IEEE1355-links (see chapter
Applications).
Interfaces
The TSS901E consists of the following blocks (See Figure 1):
1.
Rastetter P. et.al., Simple Interprocessor Communication Protocol Specification, DIPSAPII-DAS-
31-01, Issue 3, 08.10.96, also available on the same web site as the users guide.
2
TSS901E
4167F–AERO–06/07
TSS901E
•
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 transmit 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.
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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 Communica-
tion 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 provid-
ing 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 purpose 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.
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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 individu-
ally for each link channel by setting the respective configuration registers via the HOCI or via the
link.
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4167F–AERO–06/07
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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:
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Wormhole routing:
This mode allows hardware routing of packets by the TSS901E.
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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 auto-
matically inserted by the TSS901E when one configured transfer from the communication
memory has finished.
1.
Rastetter P. et.al., Simple Interprocessor Communication Protocol Specification, DIPSAPII-DAS-
31-01, Issue 3, 08.10.96, also available on the same web site as the users guide.
4
TSS901E
4167F–AERO–06/07
TSS901E
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 (µCon-
troller, 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 functionality,
the principal blocks of the PPU and their function are described here. This functionality is pro-
vided for every DS link channel of the TSS901E.
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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 mismatch, wrong
commands or disabled safety critical "simple control commands".
The protocol execution unit is disabled in "transparent" or “wormhole routing” operation
mode.
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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 sending of
acknowledges from receiving new data when the transmit path is currently occupied by a
running packet transmission.
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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 Command
Interface (PRCI).
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