PM7344 S/UNI-MPH
DATA SHEET
PMC-950449
ISSUE 6
MULTI-PHY USER NETWORK INTERFACE
Pin Name
Type
Pin Function
No.
TCAMPH
I/O
62
Transmit Multi-Phy Cell Available (TCAMPH).
The TCAMPH signal is output on this pin when
input MPHEN is high. This signal indicates
when a cell is available in the transmit FIFO for
the port selected by TWA[1:0]. When high,
TCAMPH indicates that the corresponding
transmit FIFO is not full and a complete cell may
be written. When TCAMPH goes low, it can be
configured to indicate either that the
corresponding transmit FIFO is near full and can
accept no more than four writes or that the
corresponding transmit FIFO is full. TCAMPH
will thus transition low on the rising edge of
TFCLK on which the 52nd or 48th byte is
sampled if the PHY being polled is the same as
the PHY in use. To reduce FIFO latency, the
FIFO depth at which TCAMPH indicates "full"
can be set to one, two, three or four cells.
TWRENB[4
]
Transmit Write Enable PHY #4 (TWRENB[4]).
The TWRENB[4] signal is input on this pin when
input MPHEN is low. TWRENB[4] is used to
initiate writes to the transmit FIFO of PHY #4.
When sampled low using the rising edge of
TFCLK (and the remaining three TWRENBs
remain high), a byte is written to PHY #4's
synchronous FIFO. When sampled high using
the rising edge of TFCLK, no write is performed.
TWRENB[4] must operate in conjunction with
TFCLK to access the FIFOs at a high enough
instantaneous rate as to avoid FIFO overflows.
The ATM layer device may deassert
TWRENB[4] at anytime it is unable to provide
another byte.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
34
PMC [ PMC-SIERRA, INC ]
