HT80C51 datasheet(91/132 Pages) ETC2

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HT80C51 User Manual

80C51 Family Instruction Set – Instruction definitions

Handshake Solutions

Page 91 of 132

6.2.

Instruction definitions

ACALL addr11

Function: Absolute Call

Description: ACALL unconditionally calls a subroutine located at the indicated address. The instruction incre-

ments the PC twice to obtain the address of the following instruction, then pushes the 16-bit result

onto the stack (low-order byte first) and increments the Stack Pointer twice. The destination ad-

dress is obtained by successively concatenating the five high-order bits of the incremented PC,

opcode bits 7-5, and the second byte of the instruction. The subroutine called must therefore start

within the same 2k block of the program memory as the first byte of the instruction following

ACALL. No flags are affected.

Example: Initially SP equals 07H. The label “SUBRTN” is at program memory location 0345 H. After execut-

ing the instruction,

ACALL SUBRTN

at location 0123H, SP will contain 09H, internal RAM locations 08H and 09H will contain 25H and

01H, respectively, and the PC will contain 0345H.

Bytes: 2

Cycles: 2

Encoding:

Operation: ACALL

(PC)

← (PC) + 2

(SP)

← (SP) + 1

(SP)

← (PC7-0)

(SP)

← (SP) + 1

(SP)

← (PC15-8)

(PC10-0)

← page address

a10

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