~ National ~ Semiconductor - Al Kossow's Bitsavers

6.0 Instruction Set Reference (Continued)
SHR
Shift Right
Syntax
SHR Rsd, b
Affected Flags
N,Z,C
Description
-register
Shifts the contents of the register Rsd b bits to the right and
places the result back into that register. Zeros are shifted in
from the left, (i.e., from the MSB). The value b may specify
from 0 to 7 bit shifts. The Carry flag contains the last bit
shifted out.
Example
Right justify the Address Stack Pointer from the Internal
Stack Pointer register (lSPI, R30.
MOVE ISP, R20 ;Load [ASP] from (lSPI
SHR R20,4 ;right justify [ASP]
Instruction Format
1 1111010111010101
. Opcode .
15 7
T-states
2
Bus Timing
Figure 7
Operation
1 1
b
4
1 1
Rsd
o
SUB
Syntax
SUB n, rsd
Subtract Immediate
Affected Flags
N,Z,C,V
-immediate, limited register
Description
Subtracts the immediate value n from the register rsd and
places the result back into the register rsd. Note that only
the active registers RO-R15 may be specified for rsd. The
value of n is limited to 8 bits; (signed range: + 127 to
-128). Negative numbers are represented using the two's
complement format.
Example
Subtract the constant 3 from register 10.
SUB 3, R10 ; R10 - 3 - R10
Instruction Format
1 0 1 0 11 1 0 1
. Opcode .
15 11
T-states
2
Bus Timing
Figure 7
Operation
rsd-n-rsd
n
rsd
3 0
TL/F/9336-15
2-121