UPSD3422 datasheet(40/293 Pages) STMICROELECTRONICS

40 / 293 page

8032 addressing modes

uPSD34xx

40/293

adding either the 16-bit PC or DPTR value to the contents of the accumulator. The value in

the accumulator is referred to as an index. The data fetched from the final location in

program memory is stored into the accumulator, overwriting the index value that was

previously stored there. For example:

9.8

Relative Addressing

This mode will add the two’s-compliment number stored in the second byte of the instruction

to the program counter for short jumps within +128 or –127 addresses relative to the

program counter. This is commonly used for looping and is very efficient since no additional

bus cycle is needed to fetch the jump destination address. For example:

9.9

Absolute Addressing

This mode will append the 5 high-order bits of the address of the next instruction to the 11

low-order bits of an ACALL or AJUMP instruction to produce a 16-bit jump address. The

jump will be within the same 2K byte page of program memory as the first byte of the

following instruction. For example:

9.10

Long Addressing

This mode will use the 16-bits contained in the two bytes following the instruction byte as a

jump destination address for LCALL and LJMP instructions. For example:

9.11

Bit Addressing

This mode allows setting or clearing an individual bit without disturbing the other bits within

an 8-bit value of internal SRAM. Bit Addressing is only available for certain locations in 8032

DATA and SFR memory. Valid locations are DATA addresses 20h - 2Fh and for SFR

addresses whose base address ends with 0h or 8h. (Example: The SFR, IE, has a base

MOVC A, @A+DPTR

; Move code byte relative to

; DPTR into accumulator

MOVC A, @A+PC

; Move code byte relative to PC

; into accumulator

SJMP 34h

; Jump 34h bytes ahead (in program

; memory) of the address at which

; the SJMP instruction is stored. If

; SJMP is at 1000h, program

; execution jumps to 1034h.

AJMP 0500h

; If next instruction is located at

; address 4000h, the resulting jump

; will be made to 4500h.

LJMP 0500h

; Unconditionally jump to address

; 0500h in program memory

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