
RELEASED 
DATASHEET 
PM7383 FREEDM-32A256
ISSUE 1 
PMC-2010336 
FRAME ENGINE AND DATA LINK MANAGER 32A256 
8.6.2 Polling Control and Management 
PROPRIETARY AND CONFIDENTIAL 
56
The TAPI256 only responds to poll addresses which are in the range 
programmed in the base address field in the TAPI256 Control register.  The 
TAPI256 uses the 3 most significant bits of the poll address for device recognition 
and the 10 least significant bits of the poll address for identification of a channel.  
The TAPI256 provides three poll results for every poll address according to Table 
7.  The TPAn[0] bit indicates whether or not space exists in the channel FIFO for 
data and the TPAn[1] bit indicates whether or not that polled channel FIFO is at 
risk of underflowing and should be provided data soon.  The TPAn[2] bit indicates 
that an underflow event has occurred on that channel FIFO. 
Table 7 – Transmit Polling 
Poll 
Address 
Channel 0 Channel 0 
Channel 1 Channel 1 
Channel 2 Channel 2 
Channel 3 Channel 3 
Channel 4 Channel 4 
Channel 5 Channel 5 
Channel 6 Channel 6 
Channel 7 Channel 7 
Channel 8 Channel 8 
Channel 
255 
TPA1[0] 
(Full/Space) 
TPA1[1] 
(Space/Starving) 
TPA1[2] 
(Underflow)
TPA2[0] 
(Full/Space)
TPA2[1] 
(Space/Starving)
TPA2[2] 
(Underflow)
Channel 0 
Channel 1 
Channel 2 
Channel 3 
Channel 4 
Channel 5 
Channel 6 
Channel 7 
Channel 8 
Channel 0
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Channel 8
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Channel 8
Channel 9
Channel 1 
Channel 2 
Channel 3 
Channel 4 
Channel 5 
Channel 6 
Channel 7 
Channel 8 
Channel 9 
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Channel 8
Channel 9
Channel 
255 
Channel 
255 
Channel 
255 
Channel 0
Channel 0 
Channel 0
The TAPI256 maintains a mirror image of the status of each channel FIFO in the 
partial packet buffer.  The THDL256 continuously reports the status of the 256 
channel FIFOs to the TAPI256 and the TAPI256 updates the mirror image 
accordingly.  The THDL256 also signals to the TAPI256 whenever an underflow 
event has occurred on a channel FIFO.  At the beginning of every data transfer 
across the Tx APPI, the TAPI256 sets the mirror image status of the channel to 
“full”.  Only the TAPI256 can cause the status to be set to “full” and only the 
THDL256 can cause the status to be set to “space” or “starving”.  Only the 
THDL256 can cause the status to be set to “underflow” and only the TAPI256 can 
clear the “underflow” status when that channel FIFO is polled.  In the event that