Maxim Integrated DS4830A Optical Microcontroller - Manual (Page 195)

DS4830A User’s Guide
195
23.5.3 – ALU Operations Using the Active Accumulator and a Source
The following arithmetic and logical operations can use any register or immediate value as a source. The active
accumulator Acc is always used as the second operand and the implicit destination. Also, Acc may not be used as
the source for any of these operations.
add A[4] ; Acc = Acc + A[4]
addc #32h ; Acc = Acc + 0032h + Carry
sub A[15] ; Acc = Acc – A[15]
subb A[1] ; Acc = Acc – A[1] - Carry
cmp #00h ; If (Acc == 0000h), set Equals flag
and A[0] ; Acc = Acc AND A[0]
or #55h ; Acc = Acc OR
xor A[1] ; Acc = Acc XOR A[1]
23.5.4 – ALU Operations Using Only the Active Accumulator
The following arithmetic and logical operations operate only on the active accumulator.
cpl ; Acc = NOT Acc
neg ; Acc = (NOT Acc) + 1
rl ; Rotate accumulator left (not using Carry)
rlc ; Rotate accumulator left through Carry
rr ; Rotate accumulator right (not using Carry)
rrc ; Rotate accumulator right through Carry
sla ; Shift accumulator left arithmetically once
sla2 ; Shift accumulator left arithmetically twice
sla4 ; Shift accumulator left arithmetically four times
sr ; Shift accumulator right, set Carry to Acc.0, set Acc.15 to zero
sra ; Shift accumulator right arithmetically once
sra2 ; Shift accumulator right arithmetically twice
sra4 ; Shift accumulator right arithmetically four times
xchn ; Swap low and high nibbles of each Acc byte
xch ; Swap low byte and high byte of Acc
23.5.5 – ALU Bit Operations Using Only the Active Accumulator
The following operations operate on single bits of the current active accumulator in conjunction with the Carry flag.
Any of these operations may use an Acc bit from 0 to 15.
move C, Acc.0 ; copy bit 0 of accumulator to Carry
move Acc.5, C ; copy Carry to bit 5 of accumulator
and Acc.3 ; Acc.3 = Acc.3 AND Carry
or Acc.0 ; Acc.0 = Acc.0 OR Carry
xor Acc.1 ; Acc.1 = Acc.1 OR Carry
None of the above bit operations will cause the auto-increment, auto-decrement, or modulo operations defined by
the accumulator pointer control (APC) register.
23.5.6 – Example: Adding Two 4-Byte Numbers Using Auto-Increment
move A[0], #5678h ; First number – 12345678h
move A[1], #1234h
move A[2], #0AAAAh
; Second number – 0AAAAAAAh
move A[3], #0AAAh
move APC, #81h
; Active Acc = A[0], increment low bit = mod 2
add A[2] ; A[0] = 5678h + AAAAh = 0122h + Carry
addc A[3] ; A[1] = 1234h + AAAh + 1 = 1CDFh
; 12345678h + 0AAAAAAAh = 1CDF0122h
23.6 – Processor Status Flag Operations
The Processor Status Flag (PSF) register contains five flags that are used to indicate and store the results of
arithmetic and logical operations. Four of these flags can be used for conditional program branching.
23.6.1 – Sign Flag
The Sign flag (PSF.6) reflects the current state of the most significant bit of the active accumulator, (Acc.15). If
signed arithmetic is being used, this flag indicates whether the value in the accumulator is positive or negative.