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MC68341 USER’S MANUAL
MOTOROLA
7.4 REGISTER DESCRIPTION AND PROGRAMMING
This section contains a detailed description of each register and its specific function as
well as flowcharts of basic serial module programming.
7.4.1 Register Description
The operation of the serial module is controlled by writing control bytes into the
appropriate registers. A list of serial module registers and their associated addresses are
shown in Figure 7-9. The mode, status, command, and clock-select registers are
duplicated for each channel to provide independent operation and control.
NOTE
All serial module registers are only accessible as bytes. The
contents of the mode registers (MR1 and MR2), CSR, and the
auxiliary control register (ACR) bit 7 should only be changed
after the receiver/transmitter is issued a software RESET
command—i.e., channel operation must be disabled. Care
should also be taken if the register contents are changed
during receiver/transmitter operations, as undesirable results
may be produced.
The registers of the serial module are discussed in the following paragraphs in
alphabetical order. The numbers in the upper right-hand corner indicate the offset of the
register from the base address specified in the module base address register (MBAR) in
the SIM41. The numbers above the register description represent the bit position in the
register. The register description contains the mnemonic for the bit. The values shown
below the register description are the values of those register bits after a hardware reset.
A value of U indicates that the bit value is unaffected by reset. The read/write status and
the access privilege are shown in the last line.
NOTE
A CPU32 RESET instruction will not affect the MCR, but will
reset all the other serial module registers as though a
hardware reset had occurred. The module is enabled when the
STP bit in the MCR is cleared. The module is disabled when
the STP bit in the MCR is set.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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