Z86L7208FSC datasheet(31/71 Pages) ZILOG

31 / 71 page

Z86C72/C92/L72/L92

Zilog

IR Microcontroller

DS97LVO0900

P R E L I M I N A R Y

6-31

External Memory (/DM). The Z86L72 addresses up to

48K bytes (minus Extended Data RAM space) of external

memory beginning at address 16384 (Figure 18). External

data memory is included with, or separated from, the ex-

ternal program memory space. /DM, an optional I/O func-

tion that is programmed to appear on P34, is used to dis-

tinguish between data and program memory space. The

state of the /DM signal is controlled by the type of instruc-

tion being executed. An LDC opcode references PRO-

GRAM (/DM inactive) memory, and an LDE instruction ref-

erences data (/DM active Low) memory.

Expanded Register File. The register file has been ex-

panded to allow for additional system control registers,

and for mapping of additional peripheral devices into the

through R15 has been implemented as 16 groups of 16

registers per group. These register groups are known as

the ERF (Expanded Register File). Bits 7-4 of register RP

select the working register group. Bits 3-0 of register RP

select the expanded register file bank. Note that expanded

also referred to as expanded register

group (Figure 19).

The upper nibble of the register pointer (Figure 21) selects

which working register group of 16 bytes in the register file,

out of the possible 256, will be accessed. The lower nibble

selects the expanded register file bank and, in the case of

the Z86L/CX2 family, banks 0, F, and D are implemented.

A 0H in the lower nibble will allow the normal register file

(bank 0) to be addressed, but any other value from 1H to

FH will exchange the lower 16 registers to an expanded

For example:

R253 RP = 00H

R0 = Port 0

R1 = Port 1

R2 = Port 2

R3 = Port 3

But if:

R253 RP = 0DH

R0 = CTRL0

R1 = CTRL1

R2 = CTRL2

R3 = Reserved

The counter/timers are mapped into ERF group D. Access

is easily done using the following example:

RP, #0DH Select ERF D for access to bank D( work-

ing register group 0)

R0,#xx

Load CTRL0

R1, #xx

Load CTRL1

R1, 2

CTRL2

→ CTRL1

RP, #7DH

Select expanded register bank D and

working register group 7 of bank 0 for access .

71H, R2

CTRL2

→ register 71H

R1, R2

CTRL2

→ register 71H

Figure 18. Data Memory Map

65535

External

Data

Memory

16,384

Not Addressable

Z86L72

and

Z86E72

versions

Z86L7208FSC Datasheet(PDF) 31 Page - Zilog, Inc.

Z86L7208FSC Datasheet(HTML) 31 Page - Zilog, Inc.

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