Z86318 Datasheet, PDF (16/26 Pages) Zilog, Inc. – Z8 MCU 8-BIT MICROCONTROLLER

Z86318
Z8^® MCU 8-Bit Microcontroller
FUNCTIONAL DESCRIPTION
Register File. The Register File consists of three I/O port
registers, 124 general-purpose registers, and 15 control
and status registers, R0-R3, R4-R127 and R241-R255, re-
spectively (see Figure 12). The Z86318 instructions can
access registers directly or indirectly via an 8-bit address
field. This allows short, 4-bit register addressing using the
Register Pointer.
In the 4-bit mode, the register file is divided into eight
working register groups, each occupying 16 continuous lo-
cations. The Register Pointer addresses the starting loca-
tion of the active working-register group (Figures 13 and
14).
LOCATION
R255
R254
R253
R252
R251
R250
R249
R248
R247
R246
R245
R244
R243
R242
R241
R128
R127
R4
R3
R2
R1
R0
Stack Pointer (Bits 7-0)
General-Purpose
Register Pointer
Program Control Flags
Interrupt Mask Register
Interrupt Request Register
Interrupt Priority Register
Ports 0-1 Mode
Port 3 Mode
Port 2 Mode
T0 Prescaler
Timer/Counter0
T1 Prescaler
Timer/Counter1
Timer Mode
Not Implemented
General-Purpose
Registers
Port 3
Port 2
Reserved
Port 0
IDENTIFIERS
SPL
GPR
RP
FLAGS
IMR
IRQ
IPR
P01M
P3M
P2M
PRE0
T0
PRE1
T1
TMR
P3
P2
P0
Figure 12. Register File
r7 r6 r5 r4
r3 r2 r1 r0
R253
(Register Pointer)
The upper nibble of the register file address
provided by the register pointer specifies
the active working-register group.
FF
Register Group F
F0
R15 to R0
7F
70
6F
60
5F
50
4F
40
3F
Specified Working
30
Register Group
2F
20
1F
Register Group 1
10
0F
Register Group 0
I/O Ports
00
The lower nibble
of the register
file address
provided by the
instruction points
to the specified
register.
R15 to R0
R15 to R4
R3 to R0
Figure 13. Register Pointer
16
PRELIMINARY