TSS901E ATMEL Corporation, TSS901E Datasheet - Page 5

• Manufacturer Part Number: TSS901E
• Description: Tripple Point to Point IEEE1355 High Speed Controller
• Manufacturer: ATMEL Corporation

TSS901E Control by Link
Wormhole Routing
PPU Functional
Description
5
TSS901E
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.
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 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.
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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 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).
Rev. C – 24-Aug-01