
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
PM7341 S/UNI-IMA-84
DATASHEET
PMC-2000223
ISSUE 4
INVERSE MULTIPLEXING OVER ATM
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
385
Figure 30
- Channelized T1 Receive Link Timing
RSCLK[n]
RSDATA[n]
B7 B8 F B1 B2 B3 B4 B5 B6 B7 B8 B1 B2 B3
TS 24
TS 1
TS 2
The timing relationship of the receive clock (RSCLK[n]) and data (RSDATA[n]) signals of
a channelized E1 link is shown in Figure 31. The receive data stream is an E1 frame
with a single framing byte (F1 to F8 in Figure 31) followed by octet bound time-slots 1 to
31. RSCLK[n] is held quiescent during the framing byte. The RSDATA[n] data bit (B1 of
TS1) clocked in by the first rising edge of RSCLK[n] after the framing byte is the most
significant bit of time-slot 1. The RSDATA[n] bit (B8 of TS31) clocked in by the last rising
edge of RSCLK[n] before the framing byte is the least significant bit of time-slot 31. In
Figure 31, the quiescent period is shown to be a low level on RSCLK[n]. A high level,
effected by extending the high phase of bit B8 of time-slot TS31, is equally acceptable.
In channelized E1 mode, RSCLK[n] can only be gapped during the framing byte. It must
be active continuously at 2.048 MHz during all time-slot bits. Time-slots can be ignored
by setting the PROV bit in the corresponding word of the receive channel provision
RAM in the RCAS block to low.
Figure 31
- Channelized E1 Receive Link Timing
RSCLK[n]
RSDATA[n]
B6 B7
F1 F2 F3 F4 F5 F6 F7 F8B1 B2 B3
TS 31
FAS / NFAS
TS 1
B8
B4 B5 B6 B7 B8 B1 B2 B3 B4
TS 2
13.4 Transmit Link Output Timing
The timing relationship of the transmit clock (TSCLK[n]) and data (TSDATA[n])
signals of a unchannelized link is shown in Figure 32. The transmit data is viewed
as a contiguous serial stream. There is no concept of time-slots in an
unchannelized link. Each eight bits is grouped together into a byte with arbitrary
byte alignment. Octet data is transmitted from most significant bit (B1 in Figure
32) and ending with the least significant bit (B8 in Figure 32). Bits are updated on
the falling edge of TSCLK[n]. A transmit link may be stalled by holding the