ibm3206k0424 ETC-unknow, ibm3206k0424 Datasheet - Page 380

• Manufacturer Part Number: ibm3206k0424
• Description: Ibm Processor For Network Resources
• Manufacturer: ETC-unknow

IBM3206K0424
IBM Processor for Network Resources
Preliminary
RXQUE Event Timestamping
When timestamp mode is set in the RXQUE Control Register, events are timestamped. When timestamping
is enabled, a timestamp event is placed in the corresponding rxq followed by the actual event. The event
information of the timestamp event carries the timestamp. The timestamp is determined from the RXQUE
Timestamp Register, RXQUE Timestamp Pre-Scaler Register, and the RXQUE Timestamp Shift Register.
If the corresponding rxq is full, both events are dropped. It is possible to lose only the timestamp event or lose
the actual event depending on the length of the queue and the timing of the dequeue operations.
RXQUE System Receive Queues
To set up a system receive queue, set the "Diagnostic-Mode" bit in the RXQUE Control Register. Next, set
the system receive queue bit in the RXQUE Properties Register. Load the upper bound and size of event
fields, as well. After this, allocate two identical buffers in system memory. Let each buffer be large enough to
contain N events (the upper bound field prescribes the value N) and initialize both to all zeros. Write one
buffer’s starting address into the RXQUE Lower Bound Register (LOBR), and write the other’s starting
address into the RXQUE Next Lower Bound Register (NLBR). Finally, reset the diagnostic mode bit in the
RXQUE Control Register. System-receive-queue setup is complete.
The first event enqueued to a system receive queue causes RXQUE to begin filling the buffer which LOBR
references. RXQUE fills the buffer’s first entry with a "System-Receive-Queue Start-of-Buffer" event whose
information is the value ‘0’. After this, RXQUE fills the buffer's second entry with the enqueued event and
writes the value ‘2’ into the RXQUE Length Register (LENR).
The second event enqueued to the system receive queue causes RXQUE to fill the buffer's third entry and
write the value ‘3’ into LENR.
The third event enqueued to the system receive queue causes RXQUE to fill the buffer's fourth entry and
write the value ‘4’ into LENR.
This continues until LENR contains the value ‘N-1’. At that time, RXQUE fills the buffer's Nth entry with a
System-receive-queue end-of-buffer event whose information is the value in NLBR. After this, RXQUE begins
filling the buffer which NLBR references. RXQUE fills its first entry with a "System-Receive-Queue
Start-of-Buffer" event whose information is the value in LOBR. After this, RXQUE copies the contents of
NLBR into LOBR and writes the value ‘1’ into LENR. Finally, RXQUE writes the value ‘0’ into NLBR. Subse-
quent events enqueued to the system receive queue fill the buffer which LOBR references. To prevent the
system receive queue from becoming full, write a non-zero value into NLBR.
The system receive queue becomes full when the value in LENR becomes ‘N-1’ while NLBR contains the
value ‘0’. At that time, RXQUE fills the buffer's Nth entry with a system-receive-queue end-of-buffer event
whose information is the value ‘0’. RXQUE writes the value N into LENR and preserves the contents of LOBR
while dropping subsequent enqueued events. To restart the system receive queue from the "full" state, write
a non-zero value into NLBR. After restarting, the next event enqueued to the system receive queue causes
RXQUE to begin filling the buffer which NLBR references. RXQUE fills the buffer's first entry with a
system-receive-queue start-of-buffer event whose information is the value preserved in LOBR. RXQUE fills
the buffer's second entry with the enqueued event. After this, RXQUE copies the contents of NLBR into
LOBR and writes the value ‘2’ into LENR. Finally, RXQUE writes the value ‘0’ into NLBR. Subsequent events
enqueued to the system receive queue fill the buffer which LOBR references. To prevent the system receive
queue from becoming full, write a non-zero value into NLBR.
The RXQUE Queues' Status Register bit "Threshold Exceeded" indicates that the value in LENR is greater
than or equal to the value in the RXQUE Threshold Register while NLBR contains the value ‘0’. To reset this
Receive Queues (RXQUE)
pnr25.chapt05.01
Page 380 of 676
August 14, 2000