MOTOROLA Chapter 26. Serial Management Controllers (SMCs) 26-23
Part IV. Communications Processor Module

Figure 26-11. Synchronization with SMSYNx

If both SMCMR[REN] and SMCMR[TEN] are set, the Þrst falling edge of SMSYN causes

both the transmitter and receiver to achieve synchronization. The SMC transmitter can be

disabled and reenabled and SMSYN can be used again to resynchronize the transmitter

itself. Section 26.2.4, ÒDisabling SMCs On-the-Fly,Ó describes how to safely disable and

reenable the SMC. Simply clearing and setting TEN may be insufÞcient. The receiver can

also be resynchronized this way.

26.4.5 Using the Time-Slot Assigner (TSA) for Synchronization

The TSA offers an alternative to using SMSYN to internally synchronize the SMC channel.

This method is similar, except that the synchronization event is the Þrst time-slot for this

SMC receiver/transmitter after the frame sync indication rather than the falling edge of

SMSYN. Chapter 14, ÒSerial Interface with Time-Slot Assigner,Ó describes how to

conÞgure time slots. The TSA allows the SMC receiver and transmitter to be enabled

simultaneously and synchronized separately; SMSYN does not provide this capability.

Figure 26-12 shows synchronization using the TSA.

SMCLK
SMSYN
SMTXD 1s are sent Five 1s are sent
TEN set
here Tx FIFO
loaded
approximately
here
Five 1s
assume
character
length
equals 5
First bit of
first 5-bit
transmit
character
(lsb)
Transmission
could begin
here if Tx FIFO
not loaded
in time
SMSYN
detected
low here
SMCLK
SMSYN
SMRXD
REN set
here or First bit
of receive
data
(lsb)
SMSYN
detected
low here
ENTER
HUNT
MODE
command
issued
NOTES:
SMCLK is an internal clock derived from an external
CLKx or a baud rate generator.
1.
This example shows the SMC receiver and transmitter2.
enabled separately. If the REN and TEN bits were set at
the same time, a single falling edge of SMSYN would
synchronize both.
SMC1 Transmit Data
SMC1 Receive Data