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hevans1944
Hop - AC8NS
Welcome to Electronics Point!
The 8085 RLC is NOT the same as the 8051 RLC.
On the 8085, RLC copies bit 7 into the carry bit, as well as into bit 0, all other bits in the accumulator moving left one position. The original value of the carry bit is lost. Think of this as a left rotation of the accumulator with bit 7 copied into the carry bit.
On the 8051, RLC rotates bit 7 through the carry bit and the carry bit is placed in bit 0. Think of this as a nine-bit left rotation with the ninth bit (the carry bit) being appended as the most significant bit to the accumulator. Thus the original carry bit is preserved in bit 0 after the RLC instruction.
On the 8085, RLC destroys the original carry bit (because carry become bit 7). On the 8051, RL is a simple rotate of the bits in the accumulator and the carry bit is not affected.
On the 8085, RAL performs the same function as the 8051 RLC instruction, as you stated.
Here is a page describing the rotate instructions for the 8085 instruction set. And here is a page describing the 8051 instruction set. A nice slide-show presentation of the 8085 instruction set, with examples, is found here. Beginning at Slide 82, the rotate instructions are described.
The 8085 RLC is NOT the same as the 8051 RLC.
On the 8085, RLC copies bit 7 into the carry bit, as well as into bit 0, all other bits in the accumulator moving left one position. The original value of the carry bit is lost. Think of this as a left rotation of the accumulator with bit 7 copied into the carry bit.
On the 8051, RLC rotates bit 7 through the carry bit and the carry bit is placed in bit 0. Think of this as a nine-bit left rotation with the ninth bit (the carry bit) being appended as the most significant bit to the accumulator. Thus the original carry bit is preserved in bit 0 after the RLC instruction.
On the 8085, RLC destroys the original carry bit (because carry become bit 7). On the 8051, RL is a simple rotate of the bits in the accumulator and the carry bit is not affected.
On the 8085, RAL performs the same function as the 8051 RLC instruction, as you stated.
Here is a page describing the rotate instructions for the 8085 instruction set. And here is a page describing the 8051 instruction set. A nice slide-show presentation of the 8085 instruction set, with examples, is found here. Beginning at Slide 82, the rotate instructions are described.
