Registers
Z Zero flag. Z is new on the C28x. It is involved in determining if the
results of certain operations are 0. It is also used for conditional
operations.
N Negative flag. N is new on the C28x. It is involved in determining if
the results of certain operations are negative. It is also used for con-
ditional operations.
V Overflow flag. V has changed names from OV on the C2xLP. It
flags overflow conditions in the accumulator.
PM Product shift mode. The PM has increased to a 3-bit register with
additional capabilities. Below is a comparison of the PM register in
the C2xLP and the C28x. Note that the register behaves differently
depending on the operational mode of the C28x device. The XSPM
instructions correspond to equivalent C2xLP instructions conver-
sion. On the C2xLP, the PM bits corresponded to no shift at reset.
On C28x, however, the PM corresponds to a left shift of 1 at reset.
Table C−2. C2xLP Product Mode Shifter
Bits Shift Value Instruction
00 no shift SPM 0
01 shift left 1 SPM 1
10 shift left 4 SPM 2
11 shift right 6 SPM 3
Table C−3. C28x Product Mode Shifter
C2xLP Source-Compatible Mode
AMODE == 1
OBJMODE = 1
PAGE0 == 0
C28x Mode
AMODE == 0
OBJMODE = 1
PAGE0 == 0
Bits
Shift Value
Instruction Shift Value Instruction
000 shift left 1 SPM +1 (or SPM 1) shift left 1 SPM +1
001 no shift SPM 0 (or SPM 0) no shift SPM 0
010 shift right 1 SPM –1 shift right 1 SPM −1
011 shift right 2 SPM –2 shift right 2 SPM −2
100 shift right 3 SPM –3 shift right 3 SPM −3
101 shift left 4 SPM +4 (or SPM 2) shift right 4 SPM −4
110 shift right 5 SPM –5 shift right 5 SPM −5
111 shift right 6 SPM –6 (or SPM 3) shift right 6 SPM −6
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