
7- 20
MC68341 USER’S MANUAL
MOTOROLA
7.4.1.1 AUXILIARY CONTROL REGISTER (ACR). The ACR selects which baud rate is
used and controls the handshake of the transmitter/receiver. This register can only be
written when the serial module is enabled (i.e., the STP bit in the MCR is cleared).
ACR
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76543210
BRG
00000
IECB
IECA
RESET:
00000000
Write Only
Supervisor/User
BRG—Baud Rate Generator Set Select
1 = Set 2 of the available baud rates is selected.
0 = Set 1 of the available baud rates is selected. Refer to 7.4.1.2 Clock-Select
Register (CSR) for more information on the baud rates.
IECB, IECA—Input Enable Control
1 = ISR bit 7 will be set and an interrupt will be generated when the corresponding bit
in the IPCR (COSB or COSA) is set by an external transition on the channel's
CTS≈ input (if bit 7 of the IER) is set to enable interrupts).
0 = Setting the corresponding bit in the IPCR has no effect on ISR bit 7.
7.4.1.2 CLOCK-SELECT REGISTER (CSR). The CSR selects the baud rate clock for the
channel receiver and transmitter. This register can only be written when the serial module
is enabled (i.e., the STP bit in the MCR is cleared).
NOTE
This register should only be written after the external crystal is
stable (XTAL_RDY bit of the ISR is zero).
CSRA, CSRB
$711, $719
76543210
RCS3
RCS2
RCS1
RCS0
TCS3
TCS2
TCS1
TCS0
RESET:
00000000
Write Only
Supervisor/User
RCS3–RCS0—Receiver Clock Select
These bits select the baud rate clock for the channel receiver from a set of baud rates
listed in Table 7-1. The baud rate set selected depends upon the ACR bit 7. Set 1 is
selected if ACR bit 7 = 0, and set 2 is selected if ACR bit 7 = 1. The receiver clock is
always 16 times the baud rate shown in this list, except when SCLK is used.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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