PM5381-BI PMC-Sierra, Inc., PM5381-BI Datasheet - Page 528

• Manufacturer Part Number: PM5381-BI
• Description: ATM UNI, Single Channel ATM PHY Interface for 2488.32Mbps
• Manufacturer: PMC-Sierra, Inc.

13.11 Setting Transparent Mode of Operation Over POS-PHY L3
13.12 Transmit PL3 DTPA Behavior
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2000489, Issue 4
6. Enter the TXSDQ Buffer Available Threshold (BT[4:0]). See Section 13.7 for details.
7. Enter the TXSDQ Data Available Threshold (DT[7:0]). See Section 13.8 for details.
8. Optionally, reset the performance monitoring counters in all blocks by writing to the S/UNI-
To send transparent data from the POS-PHY L3 bus, configure the S/UNI-2488 for Packet Over
SONET mode as in Section 13.10 with the following amendments:
1. Set the DELINDIS bits and clear the CRC_SEL bits of the TCFP and RCFP.
2. Make sure that the FIFO on the transmit side will never underrun. A FIFO underrun in
3. Data should be transferred over the POS-PHY Level3 bus broken up into 64 byte packets
The DTPA signal gives the status of the FIFO which is being filled by the transmit PL3 interface.
When DTPA is logic 1, it indicates that the FIFO has enough room to absorb a pre-determined
number of data transfers. Once the FIFO threshold has been exceeded, meaning that the FIFO
can no longer absorb the pre-determined number of data transfers, then DTPA will transition to
logic 0.
The following diagrams show the behavior of DTPA when the FIFO threshold is reached. It is
critical that the upstream device respond properly in order to avoid any FIFO overflows in the
TXSDQ.
There are two basic methods of transferring data across the PL3 interface: burst-transfer mode,
and word-transfer mode. Burst-transfer mode is similar to the UL3 interface. Where the UL3
interface will transfer one cell at a time, the PL3 interface will transfer a maximum number of
bytes or end at an end-of-packet indication in one burst, whichever comes first. Setting
TPAHOLD (register 788H TXPHY Configuration) to logic 1 will configure the S/UNI-2488 to
burst-transfer mode.
Word-transfer mode has no such limitations. The upstream device is expected to watch the DTPA
signal to find when it can begin a transfer. Once the transfer is started, it must observe the DTPA
signal and pause when required to prevent overflowing the FIFO. Setting TPAHOLD to logic 0
will configure the S/UNI-2488 to word-transfer mode or hybrid word/burst-transfer mode.
2488 Identity and Global Performance Monitor Update register. TIP remains high as the
performance monitoring registers are loaded, and is set to a logic zero when the transfer is
complete.
Transparent mode would result in data corruption.
S/UNI-2488 Telecom Standard Product Datasheet
Released
528