PM7385 FREEDM-84A672
DATA SHEET
PMC-1990114
ISSUE 6
84 LINK, 672 CHANNEL FRAME ENGINE AND DATA LINK MANAGER
WITH ANY-PHY PACKET INTERFACE
Figure 22 – Transmit APPI Timing (Polling)
TXCLK
Dev 0
CH 254
Dev 1
TXADDR[12:0]
CH 671
CH 0
CH 8
CH 0
NULL
CH 0
CH 399
NULL
Dev 0
CH 254
Dev 1
CH 0
TPA1[0]
TPA1[1]
TPA1[2]
CH 671
HUNGRY
OK
CH 8
STARVE
OK
CH 0
HUNGRY
OK
CH 399
STARVE
UFLOW
STARVE
UFLOW
HUNGRY
OK
STARVE
OK
Dev 0
Dev 1
CH 1
TPA2[0]
TPA2[1]
TPA2[2]
CH 0
STARVE
OK
CH 1
HUNGRY
OK
CH 255
STARVE
UFLOW
CH 9
HUNGRY
OK
CH 1
HUNGRY
OK
CH 400
STARVE
UFLOW
HUNGRY
OK
Polling is completely decoupled from device and channel selection on the Tx
APPI. Accordingly, the TXADDR[12:0] signals continue to provide only a poll
address for any of the FREEDM-84A672 devices sharing the Tx APPI. The most
significant three bits provide the device address and the least significant ten bits
provide the channel address. Poll results are returned on the TPAn[2:0] signals.
The TPAn[0] bit indicates whether or not space exists in the channel FIFO for
data (high means space exists in the channel FIFO) and the TPAn[1] bit indicates
whether or not that polled channel FIFO is at risk of underflowing and should be
provided data soon (high means the channel FIFO is at risk of underflowing).
The TPAn[2] bit indicates whether or not an underflow condition has occurred on
the polled channel FIFO (high means an underflow condition occurred on that
channel). In Figure 22, channel 671 in device 0 reports that space does not exist
for data in the channel FIFO, that there is currently no risk of underflow on that
channel (hungry) and that an underflow event has not occurred on this channel
since the last poll. Channel 0 in device 0 reports that space exists for data in the
channel FIFO, that there is currently a risk of underflow on that channel (starving)
and that an underflow event has occurred on this channel since the last poll.
Polled results for two channels provide a two fold increase in the polling
bandwidth on the Tx APPI to accommodate the high density of 672 channels.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
217
PMC [ PMC-SIERRA, INC ]
