Flags Register:
Flags Register The ALU influences a number of flip flops called flags which store information related to the results of arithmetic and logical operations. Taken together this flags constitute a flag register. The Flag register is a Special Purpose Register and is completely different from the other registers in a microprocessor. Flag register is an 8-bit register accessible to the user through instruction. Each bit in the flag register has a specific function.The other 3 are left vacant and are in the future Intel versions. Therefore, 8085 has five flags - Sign flag, Zero flag, Auxillary carry flag, Parity flag and the Carry flag. Only 5 bits out of 8 bits are used as shown below: D7 D6 D5 D4 D3 D2 D1 D0 S Z X AC X P X CY The three crossed bit are redundant bits and not used. They can be either ‘0’ or ‘1’ but normally they are forced to be zero. The other five bits are affected a