tdat04622 ETC-unknow, tdat04622 Datasheet - Page 20

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

for Version 1 and 1A of the Device
UTOPIA (UT)
UT14. Nonfunctional RxPA Signal for Channels B and D in Packet Direct Status MPHY Mode
When using MPHY direct status for all operational modes (8-bit, 16-bit, and 32-bit), the RxPA signal for channels B
and D is not functional. The RxPA signal is functional only for channels A and C.
Workaround
The TDAT UTOPIA interface currently has nonfunctioning RxPAB and RxPAD output signals when used in four-
channel Multi-PHY mode as shown in Figure 1. The result of this problem is the unavailability of direct status polling
on the receive-side UTOPIA interface. To work around this problem, the following analysis is done to aid the user in
doing a round-robin data extraction procedure.
The rate at which data fills and drains the receive-side UTOPIA FIFOs is calculated as follows:
I
I
I
I
I
18
The data enters each UTOPIA FIFO from the data engine bytewise running on a 77.76 MHz system clock.
If we assume each channel (worst case) is filled with an STS-12c rate signal, then the amount of data (excluding
SONET overhead, both section/line, path, and three stuff columns) per second is
(87 x12 x 9 x 8000) – (4 x 9 x 8000) = 74.88 Mbytes/STS-12c/s or 599.040 Mbits/STS-12c/s.
Since each FIFO contains a maximum of 256 bytes/FIFO, it takes on average
(256/74,880,000) = 3.4188 µs to fill a FIFO, and with a clock cycle of 77.76 MHz, it requires as a worst case,
3.2922 µs to fill the FIFO.
Since there are four FIFOs all receiving data at 74.88 Mbytes/s, then the total bandwidth requirements of all four
channels combined is (4 x 74,880,000) = 299.52 Mbytes/s.
The servicing rate on each FIFO is based on the UTOPIA interface width and frequency. If we assume a
32-bit A/B UTOPIA interface operating at 100 MHz, then the service rate is 400 Mbytes/s to service all the
channels.
(continued)
INGRESS CHANNEL A FIFO
INGRESS CHANNEL B FIFO
INGRESS CHANNEL C FIFO
INGRESS CHANNEL D FIFO
Figure 1. Receive-Side UTOPIA Interface and Channel FIFOs
256 bytes DEEP
256 bytes DEEP
256 bytes DEEP
256 bytes DEEP
X
X
A
B
C
D
32-bit INTERFACE (A AND B)
R
R
R
R
X
X
X
X
PAA
PAB
PAC
PAD
Agere Systems Inc.
May 2001
1664 (F)