Z86L825 Datasheet, PDF (27/79 Pages) Zilog, Inc. – 20-Pin Low-Voltage IR Microcontrollers

Z86L825/826/827
20-Pin Low-Voltage IR Microcontrollers
20
16 banks of 16 registers per bank. 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: An expanded register bank is also referred to as an expanded
register group (see Figure 11).
The upper nibble of the register pointer (Figure 12 on page 22) selects which
working register group of 16 bytes in the register file, out of the possible 256, is
accessed. The lower nibble selects the expanded register file bank and, in the
case of the Z86L82X family, banks 0, F, and D are implemented. A 0h in the lower
nibble allows the normal register file (bank 0) to be addressed, but any other value
from 1h to Fh exchanges the lower 16 registers to an expanded register bank. For
example, for the Z86L82X (see Figure 11):
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 performed
using the following:
LD
RP, #0Dh ; Select ERF D for access to bank D
; (working register group 0)
LD
R0,#xx
; load CTRL0
LD
1, #xx
; load CTRL1
LD
R1, 2
; CTRL2→CTRL1
LD
RP, #0Dh ; Select ERF D for access to bank D
; (working register group 0)
LD
RP, #7Dh ; Select expanded register bank D
; working register group 7 of bank 0
; for access.
LD
71h, 2
; CTRL2→register 71h
LD
R1, 2
; CTRL2→register 71h
PS008808-1203
PRELIMINARY