tdat04622 ETC-unknow, tdat04622 Datasheet - Page 118

• Manufacturer Part Number: tdat04622
• Description: Tdat Sonet/sdh 155/622/2488 Mbits/s Data Interfaces
• Manufacturer: ETC-unknow

TDAT042G5 SONET/SDH
155/622/2488 Mbits/s Data Interface
Functional Description
UTOPIA (UT) Interface Block
UT Receive Input Path (Ingress) (continued)
Receive Cell/Packet Available (RxPA). This signal indicates when the TDAT042G5 receive FIFO can send data
to the master device. The RxPA[D:A] signal behavior depends on the provisioned low watermark in the UTOPIA
interface.
I
I
I
I
I
I
* ATM Forum Technical Committee, UTOPIA Level 3, STR-PHY-UL3-01.00, July 1999.
90
One-Cycle Delay Mode. This mode follows the UTOPIA Level 2 Standard. The RxPA response occurs one cycle
after the address is polled. RxENB is asserted to activate the selected PHY. RxDATA and RxSOP are output one
cycle after RxENB is sampled active by the PHY device.
Two-Cycle Delay Mode. This mode follows the UTOPIA Level 3 baselined text*. The RxPA response occurs two
cycles after the address is polled. RxENB is asserted to activate the selected PHY. RxDATA and RxSOP are out-
put two cycles after RxENB is sampled active by the PHY device.
RxPA[D:A] Assertion. RxPA[D:A] goes high (is asserted) when the amount of data in the receive FIFO has
reached or exceeded the low watermark or there is end of packet (EOP) resident in the FIFO.
RxPA[D:A] Deassertion. In ATM mode, the RxPA[D:A] signal goes low (is deasserted) when the FIFO has less
than the low threshold amount of data and there is no EOP inside the FIFO (i.e., part of an ATM cell). Once the
last byte of the current cell is transmitted, and if the amount of data within the FIFO is still less than the low
threshold, RxPA[D:A] is deasserted.
In packet mode, the RxPA[D:A] signal goes low (is deasserted) when the FIFO has less than the low threshold
amount of data and there is no EOP inside the FIFO.
Once the data transfer begins (since the amount of data has reached or exceeded the low watermark), and if
there is no EOP below the low threshold (i.e., a long packet), the RxPA signal is deasserted when the FIFO is
drained by the UTOPIA master device. In this case, the master must closely monitor the RxPA[D:A] signals and
use these signals as data valid indicators to ensure that bad data is not read from the TDAT042G5. TDAT042G5
will deassert the RxPA[D:A] signal immediately when the FIFO is drained.
Data Transfer. A TDAT042G5 ingress channel sends data when it has asserted RxPA[D:A] and the master
device requests data (via RxENB[D:A]). In ATM mode, if the master device requests data using RxENB[D:A] and
if the TDAT042G5 has less than the low watermark amount of data to send and there is no end of cell in the FIFO
(RxPA[D:A] is deasserted), then the TDAT042G5 UTOPIA interface will send out data that should be ignored by
the master, i.e., it does not send data from its internal FIFO.
In ATM mode, once an ATM cell transfer starts, the Tx or Rx side must complete the transfer. If the transfer is not
completed, then the cell will be corrupted. The transfer continues until either (1) the end of cell is reached, when
the end of cell exists below the low watermark, or (2) the end of the FIFO is reached. If the end of the FIFO is
reached, no underflow is flagged on the receive side. In ATM mode, the low watermark should be set so that at
least one entire cell is in the FIFO prior to asserting RxPA[D:A].
In packet mode, once the data transfer begins, the RxPA[D:A] signal will remain asserted until the FIFO is
drained if there is no EOP below the low watermark. During the time RxPA[D:A] is asserted, valid data is being
transferred.
RxPA[D:A] is updated on the rising edge of RxCLK[D:A].
In 32-bit mode, only the RxPA[A] pin of port A is used to indicate the packet/cell available status.
MPHY Support. When the RxPA signals are used for MPHY direct status, the corresponding
RxCLK[B, C, and/or D] must be provided. This clock will be the same as RxCLK[A].
(continued)
(continued)
Agere Systems Inc.
Data Sheet
May 2001