Z86C9620VSC datasheet(22/46 Pages) ZILOG

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Z86C61/62/96

Z8® MICROCONTROLLER

FUNCTIONAL DESCRIPTION (Continued)

Expanded Register File. The register file has been ex-

panded to allow for additional system control registers,

and for mapping of additional peripheral devices along

with I/O ports into the register address area. The Z8

implemented as 16 groups of 16 registers per group.

These register groups are known as the ERF (Expanded

the Expanded Register File at Bank F. The rest of the

Expanded Register is not physically implemented and is

open for future expansion.

The upper nibble of the register pointer (Figure 20) selects

which group of 16 bytes in the register file, out of the full

256, will be accessed. The lower nibble selects the ex-

panded register file bank and in the case of the Z86C61/

62/96, only Bank F is implemented. A 0H in the lower nibble

will allow the normal register file to be addressed, but any

other value from 1H to FH will exchange the lower 16

registers in favor of an expanded register group of 16

registers.

For example:

Z86C61: (See Figures 18 and 19)

R253 RP = 00H

R0 = Port 0

R2 = Port 2

R1 = Port 1

R3 = Port 3

But If:

R253 RP = 0FH

R0 = Reserved

R1 = Reserved

R2 = Port 4

R3 = Port 4, Direction Register

R9 = Port 6, Mode Register

Further examples:

SRP #0FH

Set working group 0 and Bank F

LD R2, #10010110

Load value into Port 4 using

working register addressing.

LD 2, #10010110

Load value into Port 4 using

absolute addressing.

LD 9, #11110000

Load value into Port 6 mode.

SRP #1FH

Set working group 1 and Bank F

LD R2, #11010110

Load value into general purpose

LD 12H, #11010110

Load value into general purpose

LD 2, #10010110

Load value into Port 4

RAM Protect. The upper portion of the RAM’s address

spaces 80FH to EFH (excluding the control registers) can

be protected from reading and writing. The RAM Protect

bit option is mask-programmable and is selected by the

customer when the ROM code is submitted. After the mask

option is selected, the user can activate from the internal

ROM code to turn off/on the RAM Protect by loading a bit

D6 in the IMR register to either a 0 or a 1, respectively. A

1 in D6 indicates RAM Protect enabled.

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