PXB4219 Datasheet, PDF (81/290 Pages) Infineon Technologies AG – IWE8 Interworking Element for 8 E1/T1 Lines

4.6
Internal Queues
PXB4219 / PXB4220 / PXB4221
Operational Description
4.6.1 Event Queue
All the functional blocks that process octets or cells can generate counter events, i.e.
commands to increment a particular counter in the external RAM. All counter events are
written in a FIFO queue that can store 256 counter events.
A counter event contains the statistics counter address in external RAM and an
increment value.
4.6.2 Output Queue
When a cell is completely stored in the ATM Receive or Segmentation Buffer, it is ready
to be transmitted to the ATM layer over the UTOPIA receive interface. The external RAM
address of the cell is stored in a common Output Queue (OQ).
The Output Queue is a First In First Out (FIFO) queue with a maximum of 256 cell
address entries. It is common to ATM and AAL mode ports.
As long as the Output Queue is not empty, the Cell Receive processing (CR) will write
the corresponding cell from external RAM to the UTOPIA Receive interface (UR).
4.6.3 Interrupt Queue
The Interrupt Queue in external RAM is handled as a FIFO which is written whenever a
counter reaches its threshold value.
When there are interrupts in the Interrupt Queue, the “iq_ne” bit in the interrupt status
register 1 “isr1” will be set to 1. When the corresponding bit is not masked in the “imr1”
register an interrupt will be generated on the MPIR1 pin.
The microprocessor should react on the interrupt by reading the Interrupt Queue. When
“oam_act” is set to 1, the MPADR(12:1) address bits are don’t care. The next Interrupt
Queue entry will automatically be provided.
Each Interrupt Queue entry identifies a particular OAM counter that has reached its
threshold value. The counter is identified by its “port_nr”, “channel_nr” and “counter_nr”.
When the microprocessor reads the counter value and the “dest_read” bit of the register
oamc is set to 1, the counter is automatically reset.
Each Interrupt Queue entry also indicates whether there are still more interrupts in the
queue in the “iq_ne” field of the interrupt status register “isr1”. This allows the software
to read the Interrupt Queue until it is empty without having to read the interrupt status
register “isr1” again.
When the statistics function is disabled (oamc[oam_act] = 0), the µP can read and write
all addresses of the Interrupt Queue.
Data Sheet
81
2002-05-06