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Chapter 21
Serial Interface
210
210
The physical interface to all SCCs and SMCs is implemented in the serial interface (SI).
The SI allows each individual SCC and SMC to be connected externally either through two
separate time-division multiplexed (TDM) interfaces or through dedicated pins in a
non-multiplexed serial interface (NMSI).
When an SCC or SMC is conÞgured to use the NMSI, the SI provides ßexible clocking
from a bank of clocks, including external clock pins and internal baud rate generators
(BRGs). See Section 21.3, ÒNMSI ConÞguration,Ó and Section 21.4, ÒBaud Rate
Generators (BRGs).Ó
Connecting the SCCs and SMCs to the multiplexed (TDM) interface is accomplished
through a set of TDM pins and a time-slot assigner (TSA). Two independent TDM channels
(TDMa and TDMb) are available. The user programs the TSA to route data from the TDM
data stream to and from the SCCs and SMCs. The TSA also provides external strobe signals
(L1ST1Ð4), which can be used to enable external devices, such as codecs, to insert or take
data from the TDM data stream. An external framer (providing receive and transmit data,
clocks, and synchronization signals) is required to interface to the TDM channels. Common
examples of TDM channels are T1 lines in the U.S. and Japan and CEPT (E1) lines in
Europe.
If the TSA is not required for routing data to and from the SCCs and SMCs, it can still be
used to generate complex waveforms on its four strobe output pins (L1ST1Ð4). For
example, the user can program the TSA to implement stepper motor control signals of
variable duty cycle and period.
MOTOROLA
Chapter 21. Serial Interface
21-1
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