
IBM2520L8767
IBM Processor for ATM Resources
Receive AAL Processing (RAAL)
Page 278 of 553
atmrm.chapt05.01
08/27/99
Shutting Down an LCD
To shut down an LCD for receive, the following steps should be followed:
1. Clear the entry for this LCD in the LCD table table (to stop receiving cells for this LCD).
2. Do an LCD update operation that sets LCD state to down.
3. Read the LCD reassembly pointer.
4. If the reassembly pointer is non-zero and LCD is set up to do cut-through, be sure to free any DMA
descriptor that was added with the cut-through operation.
5. If reassembly pointer is non-zero, free it to POOLs.
6. If reassembly pointer is non-zero, decrease the reassembly count by writing the reassembly count regis-
ter.
If reassembly timeout is being used, the following sequence can be used:
1. Clear the entry for this LCD in the LCD table table (to stop receiving cells for this LCD).
2. Wait for reassembly timeout event.
3. If set up for cut-through, a DMA canceled event will also flow.
4. At this point, do an LCD update operation that sets LCD state to down.
5. If set up to receive the packet address in the event, free it to POOLS.
Performing an LCD Shutdown of a Cut-Through LCD
There are two possibilities here. The first uses the timeout feature and is immeasurably preferable since it
makes the best use of the on-chip mechanisms for resource allocation and control. To shut down the
cut-through LCD, use the following procedures.
Using the Timeout Feature
The key here is to use the Reassembly Timeout feature. One can shut down 100s or 1000s of LCDs and then
wait for a short time (approximately 100 microseconds) and everything will return to normal.
You may use the second set of Reassembly Timeout registers allowing you to leave the first set alone and
use the second set for the shutdown mechanism.
1. Clear the LCDs entry in the LCD table table (the VCI to LCD translate table in REASM, offset 0x161C).
This halts cell reception for this LCD.
2. Flush the REASM cache.
3. Wait for the Reassembly Timeout event (see Note below). IBM2520L8767 now cleans up resources used
for this LCD.
4. If the LCD is set for cut-through AND it has a DMA descriptor enqueued to the packet, awaiting packet
completion, a DMA Cancelled event will follow the Reassembly Timeout.
5. Now the state of the LCD can be checked to determine if it is ’Error’ or ’Idle’. Either way, the LCD is now
shut down and any other administrative processing may be done.
6. Using the LCD Update Operation Register (RAALL), set the state of the LCD to ’DOWN’. This is the
’state’ field of the Receive LCD and it is set to 0x00.