MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 17-1
Chapter 17 Baud-Rate Generators (BRGs)
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 BRGs’ main features:
Eight independent and identical BRGs
On-the-fly 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 17-1 shows a BRG.
Figure 17-1. Baud-Rate Generator (BRG) Block Diagram
Each BRG clock source can be BRGCLK, or a choice of two external clocks (selected in BRGCx[E XTC]).
The BRGCLK is an internal signal generated in the PowerQUICC II clock synthesizer specifically for the
BRGs, the SPI, and the I2C internal BRG. Alternatively, external clock pins can be configured as clock
sources. The external source option allows flexible baud-rate frequency generation, independent of the
system frequency. Additionally, the external source option allows a single external frequency to be the
CLK Pin x Clock
Source
MUX
Divide by
1 or 16
Prescaler
12-Bit Counter
1–4,096
DIV 16 CD[0–11]
BRGO
n
Clock
BRGCLK
EXTC
ATB
Autobaud
Control
RXD
n
To Pin and/or
Bank of Clocks
BRG
n
CLK Pin y