Z08617 Datasheet, PDF (11/26 Pages) Zilog, Inc. – NMOS Z8 8-BIT MCU KEYBOARD CONTROLLER

Z08617 NMOS Z8^® 8-BIT MCU
KEYBOARD CONTROLLER
FUNCTIONAL DESCRIPTION (Continued)
Register File. The register file (Figure 10) consists of four
I/O port registers, 124 general-purpose registers and 16
control and status registers (R3-R0, R127-R4, and R255-
R240, respectively). The instructions can access registers
directly or indirectly through an 8-bit address field. This
allows short, 4-bit register addressing using the Register
Pointer (Figure 11). In the 4-bit mode, the register file is
divided into nine working-register groups, each occupy-
ing 16 continuous locations. The Register Pointer ad-
dresses the starting location of the active working-register
group.
LOCATION
R255
R254
R253
R252
R251
R250
R249
R248
R247
R246
R245
R244
R243
R242
R241
R240
R127
R4
R3
R2
R1
R0
Stack Pointer (Bits 7-0)
General-Purpose Register (Bits 7-0)
Register Pointer
Program Control Flags
Interrupt Mask Register
Interrupt Request Register
Interrupt Priority Register
Ports 1-0 Mode
Port 3 Mode
Port 2 Mode
T0 Prescaler
Timer/Counter0
T1 Prescaler
Timer/Counter1
Timer Mode
Reserved
Not Implemented
General-Purpose
Registers
Port 3
Port 2
Port 1
Port 0
IDENTIFIERS
SPL
GPR
RP
FLAGS
IMR
IRQ
IPR
P01M
P3M
P2M
PREQ
T0
PRE1
T1
TMR
P3
P2
P1
P0
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
•
•
•
•
•
Specified Working
•
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 11. Register Pointer Configuration
Figure 10. Register File Configuration
11