Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

8051 HANEL

REGISTER BANKS AND STACKRegister Banks (cont’)

‰We can switch to other banks by use of the PSW register

¾Bits D4 and D3 of the PSW are used to select the desired register bank¾Use the bit-addressable instructions SETB and CLR to access PSW.4 and PSW.3

1

1

Bank 3

0

1

Bank 2

1

0

Bank 1

0

0

Bank 0

RS0(PSW.3)

RS1(PSW.4)

PSW bank selection