MICROPROCESSOR AND MICROCONTROLLER

Detailed explanation-1: -Explanation: If RS1=1, RS0=1, then the register bank selected is register bank 3.

Detailed explanation-2: -How to Switch Register Banks. Register bank 0 is the default when the 8051 is powered up. We can switch to the other banks using PSW register. D4 and D3 bits of the PSW are used to select the desired register bank, since they can be accessed by the bit addressable instructions SETB and CLR.

Detailed explanation-3: -If RS1=0, RS0=0, then selected bank is register bank 0.

Detailed explanation-4: -The bits RS0 and RS1 are used to change the bank registers. The following figure shows the program status word register. The PSW Register contains that status bits that reflect the current status of the CPU. Flag 0 available to user for general purpose.

Detailed explanation-5: -The two bits of PSW are used for switching between the register banks. These two bits are accessed by the bit-addressable instructions SETB and CLR. Based on the possible combinations of RS1 and RS0 of PSW, the register bank is changed accordingly, i.e., if RS1 and RS0 are 0, then the Bank 0 is selected.