Z86L79 datasheet(21/58 Pages) ZILOG

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Z86L79/80

Low-Voltage Microcontroller

Zilog

3-21

P R E L I M I N A R Y

DS97LVO0601

FUNCTIONAL DESCRIPTION (Continued)

isters, 236 general-purpose registers with 10 control and

status registers (R3-R0, R239-R4, and R255-R246, re-

spectively), plus three Expanded Register Groups (0, D,

and F) which reside in the expanded register group. In-

structions can access registers directly or indirectly

through an 8-bit address field. This allows a short, 4-bit

the 4-bit mode, the register file is divided into 16 working

The Register Pointer addresses the starting location of the

active working register group.

Note: Register Bank E0-EF is only accessed through

working registers and indirect addressing modes. R240-

R245 registers are reserved.

Stack. The Z86L7X external data memory or the internal

(R255) is used for the internal stack that resides within the

general-purpose registers (R4-R239). SPH is used as a

general-purpose register only when using internal stacks.

Note: When SPH is used as a general-purpose register

and Port 0 is in address mode, the contents of SPH will be

loaded into Port 0 whenever the internal stack is accessed

Figure 16. Register Pointer

D5 D4

Expanded Register

File Pointer

Working Register

Pointer

R253 RP

Default Setting After Reset = 0000 0000

Figure 17. Register Pointer

The upper nibble of the register file address

provided by the register pointer specifies

the active working-register group

R253

I/O Ports

Specified Working

The lower nibble

of the register

file address

provided by the

instruction points

to the specified

R15 to R4

R3 to R0

R15 to R0

Z86L79 Datasheet(PDF) 21 Page - Zilog, Inc.

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