User manual

µPD750008 USER'S MANUAL

4.5 GENERAL REGISTER: 8 x 4 BITS x 4 BANKS

The general registers are mapped to particular addresses in data memory. Four banks of registers are

provided, with each bank consisting of eight 4-bit registers (B, C, D, E, H, L, X, and A).

The register bank (RB) to be enabled at the time of instruction execution is determined by:

RB = RBE·RBS: (RBS = 0 to 3)

Each general register allows 4-bit manipulation. In addition, BC, DE, HL, or XA serves as a register pair

for 8-bit manipulation. DL also makes a register pair as well as DE and HL. These three register pairs can

be used as data pointers.

In 8-bit manipulation, the register pairs in the register banks (0 <—> 1, 2 <—> 3) that have the inverted

value of bit 0 of the register bank (RB) address can be specified as BC’, DE’, HL’, and XA’ in addition to the

A general register area can be addressed and accessed as normal RAM, regardless of whether it is used

as a register.

Figure 4-8. General Register Format

Address

000H

001H

002H

003H

004H

005H

006H

007H

008H

00FH

010H

017H

018H

01FH

A register

X register

L register

H register

E register

D register

C register

B register

Same as bank 0

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Data memory