RS8234EBGC Mindspeed Technologies, RS8234EBGC Datasheet - Page 131

• Manufacturer Part Number: RS8234EBGC
• Description: RS8234EBGC ATM XBR SAR
• Manufacturer: Mindspeed Technologies

RS8234
ATM ServiceSAR Plus with xBR Traffic Management
5.4.9 Hardware PDU Time-out
28234-DSH-001-B
5.4.8.7 Error Conditions
5.4.8.6 AAL3/4 Early
5.4.9.1 Reassembly
Time-out Process
Packet Discard
Processing
The RS8234 performs EPD for AAL3/4 CPCS-PDUs with these steps:
Partially reassembled CPCS-PDU’s will be recovered for the following error
conditions:
The RS8234 automatically detects active CPCS-PDU time-out for reassembly
channels. A PDU time-out occurs when a partially received PDU does not
complete within a set time period. When it detects this time-out condition, the
RS8234 provides a status queue indication to the host. This indication allows the
host to recover the buffers held by the partially completed PDU. The RS8234
supports up to eight reassembly time-out periods.
A background hardware process performs the reassembly time-out function. The
process is activated at a user-selected interval. The time-out process is enabled by
setting the GTO_EN bit in the RSM_CTRL0 register. The RSM_TO register
controls the process activity once enabled. The process is activated every
RSM_TO_PER rising edges of SYSCLK on cell boundaries.
NOTE:
TO_VCC_INDEX. This is a 16-bit variable located at address 0x1350, in internal
SRAM. The host should initialize this register to zero at system initialization.
in the VCC Table entry. The host also assigns one of eight time-out periods to
each VCC by initializing the TO_INDEX field in the VCC Table entry.
ACT_PDU, to see if time-out processing is enabled and necessary, respectively,
for the current connection. If either bit is zero, then TO_VCC_INDEX is
incremented by one and compared to RSM_TO_CNT in the RSM_TO register. If
TO_VCC_INDEX = RSM_TO_CNT, then TO_VCC_INDEX is reset to zero and
the time-out search is restarted at the beginning of the VCC Tables.
Table entry. Then it compares CUR_TOCNT to the time-out value selected,
TERM_TOCNTx, where x = TO_INDEX. TERM_TOCNT0 through
TERM_TOCNT7 are located at address 0x1340 through 0x134c in internal
SRAM. They must be initialized to appropriate values during system
initialization.
• Sets the appropriate error bit in the PDU_CHECKS field for a new RSM
• Sets the CPCS_LENGTH field to zero.
• Sets the BD_PNTR field to point to the partially reassembled PDU.
• Writes the Status Queue entry.
• Discards all cells of that PDU up to and including the EOM cell for that
• Non-EOM Max PDU Length exceeded
• Free buffer queue underflow
• Status queue overflow
Each time the process is activated, it examines a single VCC, identified by
To enable hardware time-out on an individual VCC, the host must set TO_EN
The RS8234 checks the TO_EN bit and the active PDU indicator bit,
If both bits are set, the RS8234 increments CUR_TOCNT in the RSM VCC
Status Queue entry.
PDU.
Note that GTO_EN set to zero resets the internal time-out interrupt
counter.
Mindspeed Technologies
™
5.0 Reassembly Coprocessor
5.4 Buffer Management
5-27