Z86C72 Datasheet, PDF (31/71 Pages) Zilog, Inc. – IR MICROCONTROLLER

Zilog
Z86C72/C92/L72/L92
IR Microcontroller
65535
External
Data
Memory
16,384
Not Addressable
Z86L72
and
Z86E72
versions
Expanded Register File. The register file has been ex-
panded to allow for additional system control registers,
1 ^{and for mapping of additional peripheral devices into the}
register address area. The Z8 register address space R0
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
register bank is 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
register bank (See Figure 19).
For example:
R253 RP = 00H
R0 = Port 0
R1 = Port 1
R2 = Port 2
R3 = Port 3
0
Figure 18. Data Memory Map
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.
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:
LD RP, #0DH Select ERF D for access to bank D( work-
ing register group 0)
LD R0,#xx Load CTRL0
LD R1, #xx Load CTRL1
LD R1, 2
CTRL2 → CTRL1
LD RP, #7DH Select expanded register bank D and
working register group 7 of bank 0 for access .
LD 71H, R2
CTRL2 → register 71H
LD R1, R2
CTRL2 → register 71H
DS97LVO0900
PRELIMINARY
6-31