Z86D86 Datasheet, PDF (27/80 Pages) Zilog, Inc. – 28-Pin Low-Voltage OTP Microcontroller

Z86D86
28-Pin Low-Voltage OTP Microcontroller
19
16 banks, with 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 21) selects which
working register group, of 16 bytes in the register file, is accessed out of the possi-
ble 256. The lower nibble selects the expanded register file bank and, in the case
of the Z86D86 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 Z86D86 (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
PS008905-0105
PRELIMINARY