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MPC563XM Reference Manual, Rev. 1
894
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
NOTE
Whenever BS = (constant) 0, its size is considered 8 bits, and all 24 bits in
B-bus are set to 0. Therefore, all operations with BS = (constant) 0 have
their size determined by AS and Destination only.
CCS field (1 bit) controls whether flags will be updated or not (
microinstruction, the operation size will be used to sample flags. In some microinstructions CCS field is
replaced by CCSV (2 bits,
). Flag sampling according to CCSV can be set as defined by the
operation size, or fixed as 8 or 16 bit operations.
NOTE
For the post-ALU rotate right operation, CCSV also determines the rotate
size: whether 8-bit, 16-bit, or determined by the operation size.
When neither CCS nor CCSV are present in the microinstruction, flags are not sampled. CCS and CCSV
do not affect the Carry update on Exchange Bit operation (see
Section 23.4.8.2.6, “Exchange Bit
control the N and Z flags.
23.4.9.2.4
B-Source Inversion
The data selected as second source (T4BBS) can be inverted (bitwise boolean NOT) before operation. This
is controlled by microinstruction field BINV (1 bit,
). A zero value for BINV activates
B-source inversion.
x
24 bits
24 bits
24 bits
Table 23-65. Flag Sampling Using CCSV field
CCSV
Meaning
00
sample flags as an 8 bit operation
01
sample flags as a 16 bit operation
10
sample flags as defined by operation size
11
do not sample flags
Table 23-66. Flag Sampling Using CCS field
CCS
Meaning
0
sample flags as defined by operation size
1
do not sample flags
Table 23-67. B-Source Inversion - BINV
BINV
Meaning
0
invert B-source
1
Table 23-64. Operation Size Determination
A Source
B Source
Destination
Operation Size