Processor Users Manual

MOTOROLA Chapter 16. Baud-Rate Generators (BRGs) 16-1
Chapter 16
Baud-Rate Generators (BRGs)
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The CPM contains eight independent, identical baud-rate generators (BRGs) that can be
used with the FCCs, SCCs, and SMCs. The clocks produced by the BRGs are sent to the
bank-of-clocks selection logic, where they can be routed to the controllers. In addition, the
output of a BRG can be routed to a pin to be used externally. The following is a list of
BRGsÕ main features:
¥ Eight independent and identical BRGs
¥ On-the-ßy changes allowed
¥ Each BRG can be routed to one or more FCCs, SCCs, or SMCs
¥ A 16x divider option allows slow baud rates at high system frequencies
¥ Each BRG contains an autobaud support option
¥ Each BRG output can be routed to a pin (BRGOn)
Figure 16-1 shows a BRG.
Figure 16-1. Baud-Rate Generator (BRG) Block Diagram
CLK Pin x
Clock
Source
MUX
Divide by
1 or 16
Prescaler
12-Bit Counter
1Ð4,096
DIV 16 CD[0Ð11]
BRGOn Clock
BRGCLK
EXTC
AT B
Autobaud
Control
RXDn
To Pin and/or
Bank of Clocks
BRGn
CLK Pin y