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The TDM channel options with their corresponding SI RAM partitioning follow:
¥ A single TDM channel with static routingÑSI RAM is divided into Rx and Tx parts.
¥ Two TDM channels with static routingÑRx and Tx RAMs are halved.
¥ A single TDM channel with dynamic routingÑRx and Tx RAMs are halved.
¥ Two TDM channels with dynamic routingÑRx and Tx RAMs are quartered.
Note that when using a single TDM channel, the entire SI RAM is available to TDMa,
whereas only the last half of each Rx or Tx RAM is accessible to TDMb; that is, the TDMb
SI RAM area always begins at byte 128 for receive and byte 384 for transmit; see
Figure 21-6. Furthermore, if the user wants to use only TDMb, the SI RAM must still be
programmed for both TDM channels (with TDMa left unitialized and disabled). Also note
that the SI RAM is uninitialized after power-onÑthe core should program them before
enabling the TDM channels.
21.2.3.1 Disabling and Reenabling the TSA
The following steps must be taken any time the TSA is disabled. These steps also apply to
changing the SI routing when the TSA is conÞgured for static frames.
1. SCC and SMC connections to the TSA must be disabled.
2. The SI conÞguration can be modiÞed.
3. SCC and SMC connections to the TSA must be reenabled.
21.2.3.2 One TDM Channel with Static Frames
In an SI conÞguration using one multiplexed channel with static frames, shown in
Figure 21-5, there are 64 entries in the SI RAM for Rx data/strobe routing and 64 entries
for Tx data/strobe routing. Note that only TDMa can use the entire SI RAM.
Figure 21-5. SI RAM Partitioning Using TDMa with Static Frames
MOTOROLA
RDM = 00
One Channel (TDMa) with Independent Rx and Tx Route
SI RAM Address:
0
(32-Bit Entries)
64 Entries
Route
255
256
64 Entries
Route
511
Chapter 21. Serial Interface
Part V. The Communications Processor Module
Framing Signals
L1RCLKa
L1RSYNCa
Rxa
L1TCLKa
L1TSYNCa
Txa
21-9
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