Maxim Integrated DS4830A Optical Microcontroller - Manual (Page 192)

DS4830A User’s Guide
192
move GR, LC[0] ; move LC[0] to the GR register
move IC, GRH ; copy the high byte into the IC register
16-Bit Destination  Concatenation (8-Bit Source, 8-Bit Source)
Two 8-bit source registers can be concatenated and stored into a 16-bit destination by using the prefix register to
hold the high order byte for the concatenated transfer. An additional cycle may be required if either source byte
register index is greater than 0Fh.
move PFX[0], IC ; load high order source byte IC into PFX
move @++SP, AP ; store @DP[0] the concatenation of IC:AP
; 16-bit destination sub-index: dst=08h
; 8-bit source sub-indexes:
; high=10h, low=11h
move PFX[1], #00h ;
move PFX[3], high ; PFX=00:high
move dst, low ; dst=high:low
Low (16-Bit Destination)  8-Bit Source
To modify only the low byte of a given 16-bit destination, the 16-bit register should be moved into the GR register
such that the high byte can be singulated and the low byte written exclusively. An additional cycle is required if the
destination index is greater than 0Fh.
move GR, DP[0] ; move DP[0] to the GR register
move PFX[0], GRH ; get the high byte of DP[0] via GRH
move DP[0], #20h ; store the new DP[0] value
; 16-bit destination sub-index: dst=10h
; 8-bit source sub-index: src=11h
move PFX[1], #00h ;
move GR, dst ; read dst word to the GR register
move PFX[5], GRH ; get the high byte of dst via GRH
move dst, src ; store the new dst value
High (16-Bit Destination)
 8-Bit Source
To modify only the high byte of a given 16-bit destination, the 16-bit register should be moved into the GR register
such that the low byte can be singulated and the high byte can be written exclusively. Additional cycles are required
if the destination index is greater than 0Fh or if the source index is greater than 0Fh.
move GR, DP[0] ; move DP[0] to the GR register
move PFX[0], #20h ; get the high byte of DP[0] via GRH
move DP[0], GRL ; store the new DP[0] value
; 16-bit destination sub-index: dst=10h
; 8-bit source sub-index: src=11h
move PFX[1], #00h ;
move GR, dst ; read dst word to the GR register
move PFX[1], #00h
move PFX[4], src
; get the new src byte
move dst, GRL ; store the new dst value
If the high byte needs to be cleared to 00h, the operation can be shortened by transferring only the GRL byte to the
16-bit destination (example follows):
move GR, DP[0] ; move DP[0] to the GR register
move DP[0], GRL ; store the new DP[0] value, 00h used for high byte
23.4 – Reading and Writing Register Bits
The MOVE instruction can also be used to directly set or clear any one of the lowest 8 bits of a peripheral register in
module 0h-5h or a system register in module 8h. The set or clear operation will not affect the upper byte of a 16-bit
register that is the target of the set or clear operation. If a set or clear instruction is used on a destination register that
does not support this type of operation, the register high byte will be written with the prefix data and the low byte will
be written with the bit mask (i.e. all 0’s with a single 1 for the set bit operation or all ones with a single 0 for the clear
bit operation).