Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

BIT HANEL

ADDRESSESRegisters

Bit-

Addressability

‰Only registers A, B, PSW, IP, IE, ACC, SCON, and TCON are bit-addressable

¾While all I/O ports are bit-addressable

‰In PSW register, two bits are set aside for the selection of the register banks

¾Upon RESET, bank 0 is selected¾We can select any other banks using the bit-addressability of the PSW

P

--

OV

RS0

RS1

--

AC

CY

18H - 1FH

3

1

1

10H - 17H

2

0

1

08H - 0FH

1

1

0

00H - 07H

0

0

0

Address

Register Bank

RS0

RS1