Maxim Integrated MAXQ610 - Manual (Page 39)

3-4
MAXQ610 User’s Guide
However, the operation:
move DP[0], #0055h
does not require a prefixing operation even though the register DP[0] is 16 bits . This is because the prefix value
defaults to zero, so the following line is not required:
move PFX[0], #00h
3.3 Reading and Writing Registers
All functions in the MAXQ610 are accessed through registers, either directly or indirectly . This section discusses load-
ing registers with immediate values and transferring values between registers of the same size and different sizes .
3.3.1 Loading an 8-Bit Register with an Immediate Value
Any writable 8-bit register with a subindex from 0h to 7h within its module can be loaded with an immediate value in a
single cycle using the MOVE instruction .
move AP, #05h ; load accumulator pointer register with 5
Writable 8-bit registers with subindexes 8h and higher can be loaded with an immediate value using MOVE as well,
but an additional cycle is required to set the prefix value for the destination .
move WDCN, #33h ; assembles to: move PFX[2], #00h
; move (WDCN-80h), #33h
3.3.2 Loading a 16-Bit Register with a 16-Bit Immediate Value
Any writable 16-bit register with a subindex from 0h to 7h can be loaded with an immediate value in a single cycle if
the high byte of that immediate value is zero .
move LC[0], #0010h ; prefix defaults to zero for high byte
If the high byte of that immediate value is not zero or if the 16-bit destination subindex is greater than 7h, an extra cycle
is required to load the prefix value for the high byte and/or the high-order register index bits .
; high byte <> #00h
move LC[0], #0110h ; assembles to: move PFX[2], #01h
; move LC[0], #10h
; destination sub-index > 7h
move A[8], #0034h ; assembles to: move PFX[2], #00h
; move (A[8]-80h), #34h
3.3.3 Moving Values Between Registers of the Same Size
Moving data between same-size registers can be done in a single-cycle MOVE if the destination register’s index is from
0h to 7h and the source register index is between 0h and 0Fh .
move A[0], A[8] ; copy accumulator 8 to accumulator 0
move LC[0], LC[1] ; copy loop counter 1 to loop counter 0
If the destination register’s index is greater than 7h or if the source register index is greater than 0Fh, prefixing is
required .
move A[15], A[0] ; assembles to: move PFX[2], #00h
; move (A[15]-80h), A[0]