Function: Absolute Call
SECTION 1 80C51 FAMILY
Description: ACALL unconditionally calls a subroutine located at the indicated address. The instruction increments the PC twice to obtain the address of the following instruction, then pushes the IS-bit result onto the stack (low-order byte first) and increments the Stack Pointer twice. The destination address is obtained by successively concatenating the five high-order bits of the incremented PC, opcode bits 7-S, 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 executing 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 034SH.
By1es: 2 Cycles: 2
Encoding:
I
al0a9 a81I
0 0 0 1Operation: ACALL (PC) ~ (PC)
+
2 (SP) ~ (SP)+
1 (SP) ~ (PC7•0) (SP) ~ (SP)+
1 (SP) ~ (PC,s.
a) (PClO-o) ~ page addressI
a7 as as a4I
a3 a2 al aO80C51 family programmer's guide and instruction set
ADD A,<src-byte>
Function: Add
SECTION 1 80C51 FAMILY
Description: ADD adds the byte variable indicated to the Accumulator, leaving the result in the Accumulator. The carry and auxiliary-carry flags are set, respectively, if there is a carry-out from bit 7 or bit 3, and cleared otherwise. When adding unsigned integers, the carry flag indicates an overflow occurred.
OV is set if there is a carry-out of bit 6 but not out of bit 7, or a carry-out of bit 7 but not bit 6; otherwise OV is cleared. When adding signed integers, OV indicates a negative number produced as the sum of two positive operands, or a positive sum from two negative operands.
Four source operand addressing modes are allowed: register, direct, register-indirect, or immediate.
Example: The Accumulator holds OC3H (11000011 B) and register 0 holds OAAH (1010101 OB). The instruction, ADD A,RO
will leave 6DH (01101101 B) in the Accumulator with the AC flag cleared and both the Carry flag and OV set to 1.
ADD A,Rn Bytes:
Cycles:
Encoding
:1
L. 0 __ 0 __ 1_0_ ... _ _ _ r _r---, Operation: ADD(A) ~ (A)
+
(Rn) ADD A,directBytes: 2 Cycles:
Encoding:
I
0 0 1 0I
0Operation: ADD
ADD A,@Ri Bytes:
Cycles:
(A) ~ (A)
+
(direct)Encoding:
1
0 0 1 0I
0 Operation: ADD(A) ~ (A)
+
((Ri)) ADD A,#dataBytes: 2 Cycles:
Encoding: 1 0 0 1 0 I 0 Operation: ADD
(A) ~ (A)
+
#datao
1o
0I
direct address1
immediate datalSignetics 80C51-Based 8-Bit Microcontrollers
80C51 family programmer's guide and instruction set
SECTION 1 80C51 FAMILY
ADDC A,<src-byte>
Function: Add with Carry
Description: ADDC simu~aneously adds the byte variable indicated, the carry flag and the Accumulator contents, leaving the result in the Accumulator. The carry and auxiliary-carry flags are set, respectively, if there is a carry-out from bit 7 or bit 3, and cleared otherwise. When adding unsigned integers, the carry flag indicates an overflow occurred.
OV is set if there is a carry-out of bit 6 but not out of bit 7, or a carry-out of bit 7 but not out of bit 6;
otherwise OV is cleared. When adding signed integers, OV indicates a negative number produced as the sum of two positive operands, or a positive sum from two negative operands.
Four source operand addressing modes are allowed: register, direct, register-indirect, or immediate.
Example: The Accumulator holds OC3H (11000011 B) and register 0 holds OAAH (10101010B) with the carry flag set.
The instruction, ADDC A,RO
will leave 6EH (0110111 OB) in the Accumulator with AC cleared and both the Carry flag and OV set to 1.
AD DC A,Rn Bytes:
Cycles:
Encoding: 10 0 1 1 11 r r Operation: ADDC
(A) (- (A)
+
(C)+
(Rn) ADDC A,directBytes: 2 Cycles:
Encoding: 10 0 1 1 10 0 1
I
direct addressI
Operation: ADDC
(A) (- (A)
+
(C)+
(direct) ADDC A,@RIBytes:
Cycles:
Encoding: 10 0 1 1 10 Operation: ADDC
(A) (- (A)
+
(C)+
«Ri)) ADDC A,#dataBytes: 2 Cycles:
Encoding: 10 0 1 1 10 0 0
I
immediate dataI
Operation: ADDC
(A) (- (A)
+
(C)+
#dataFebruary 1992
Signetics 80C51-Based 8-Bit Microcontrollers
80C51 family programmer's guide and instruction set
AJMP addr11
Function: Absolute Jump
SECTION 1 80C51 FAMILY
Description: AJMP transfers program execution to the indicated address, which is formed at run-time by concatenating the high-order five bits of the PC (after incrementing the PC twice), opcode bits 7-5, and the second byte of the instruction. The destination must therefore be within the same 2k block of program memory as the first byte of the instruction following AJMP.
Example: The label "JMPADR" is at program memory location 0123H. The instruction, AJMP JMPADR
is at location 0345H and will load the PC with 0123H.
Bytes: 2 Cycles: 2
Encoding:
I
al0 a9 a8 0 0 0 0 1I
a7 a6 as a4 a3 a2 al aO Operation: AJMP(PC) (- (PC)
+
2 (PC,().o) (-page addressANL <dest-byte>,<src-byte>
Function: Logical-AND for byte variables
Description: ANL performs the bitwise logical-AND operation between the variables indicated and stores the results in the destination variable. No flags are affected.
The two operands allow six addressing mode combinations. When the destination is the Accumulator, the source can use register, direct, register-indirect, or immediate addressing; when the destination is a direct address, the source can be the Accumulator or immediate data.
Note: When this instruction is used to modify an output port, the value used as the original port data will be read from the output data latch, not the input pins.
Example: If the Accumulator holds OC3H (110000118) and register 0 holds 55H (010101018) then the instruction, ANL A,RO
February 1992
will leave 41 H (010000018) in the Accumulator.
When the destination is a directly addressed byte, this instruction will clear combinations of bits in any RAM location or hardware register. The mask byte determining the pattern of bits to be cleared would either be a constant contained in the instruction or a value computed in the Accumulator at run-time. The instruction,
ANL Pl,#0111001B
will clear bits 7, 3, and 2 of output port 1.
67
Signetics 80C51-Based 8-Bit Microcontrollers