TSS901E_07 ATMEL Corporation, TSS901E_07 Datasheet - Page 5

• Manufacturer Part Number: TSS901E_07
• Description: Triple Point to Point IEEE 1355 High Speed Controller
• Manufacturer: ATMEL Corporation

TSS901E Control
by Link
Wormhole Routing
PPU Functional
Description
4167F–AERO–06/07
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.
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.
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.
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.
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).
TSS901E
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