PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
addresses 24 through 30. This is typically used to allow more than one slave
device to share the Transmit Any-PHY/UTOPIA master bus.
In the Any-PHY slave mode, the transmit interface of the S/UNI-IMA-8 appears
as a multi-PHY device with 8 ports used for the data path where all ports are
identified in the in-band address. The configuration register TCAEN controls the
response to polling the individual channels. Setting high on TCAEN[0] enables
addresses 0 through 7, and TCAEN[3] enables addressed 24 through 31. This is
typically used to allow more than one slave device to share the Transmit Any-
PHY/UTOPIA master bus.
Conceptually, the Any-PHY protocol can be divided into two processes: polling
and cell transfer.
Polling in the transmit direction is used by the bus master – typically a traffic
buffering and management device – to determine when a buffered data cell can
be safely sent to a PHY (or to a virtual PHY in the case of the S/UNI-IMA-8). The
S/UNI-IMA-8 provides an independent 3-deep cell buffer FIFO for each virtual
PHY. In total, there are 8 FIFOs. This arrangement ensures that there is no head-
of-line blocking.
The traffic manager need only poll those virtual PHYs for which it has cells
queued. A cell transfer can be initiated after a polled virtual PHY asserts the TPA
output. Each virtual PHY’s cell buffer availability status (i.e., the status that will be
driven onto the TPA output when the virtual PHY is polled) is deasserted when
the first byte of the last cell is written into the buffer. It is re-asserted only when
the FIFO can accept another complete cell.
In Any-PHY mode, polling is performed using the TADR[10:0] bus in conjunction
with the TCSB. Each S/UNI-IMA-8 uses the TADR[2:0] bits to indicate the 8
logical virtual PHYs. The upper bits from the TADR bus, TADR[6:3], are
compared to the configured address to select the device. The remaining address
bits from the traffic manager are decoded externally and are used to drive the
TCSB. The address prepend field in the cell transfer contains the entire 16-bit
address. In 8-bit mode, the prepend address is reduced to 8-bits.
In Any-PHY mode, the cell transfer is initiated after a successful poll. The virtual
PHY address is prepended to the cell, thus performing an inband selection. The
S/UNI-IMA-8 monitors the address prepend on the cell transfer to detect its cells.
For UTOPIA L2 Mode, Only TADR[4:0] are used for polling and selection. Each
FIFO will only assert TCA when polled if it is not in the process of transferring a
cell and if there is room in the FIFO for a complete cell. Unlike Any-PHY, in
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
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PMC [ PMC-SIERRA, INC ]
