Z86L70 Datasheet, PDF (22/61 Pages) Zilog, Inc. – IR/Low-Voltage Microcontroller

Z86L70/71/75/C71
IR/Low-Voltage Microcontroller
R253 RP
D7 D6 D5 D4 D3 D2 D1 D0
Default Setting After
Reset = 0000 0000
Expanded Register Bank
File Pointer
Working Register
Pointer
Figure 15. Register Pointer
RAM/Register File. The register file (group 0) consists of
four I/O port registers, 236 general purpose registers, and
16 control and status registers (R0-R3, R4-R239, and
R240-R255, respectively), plus two expanded registers
group (Banks D and F). In the 4-bit mode, the register file
is divided into 16 working register groups, each occupying
16 continuous locations. The Register Pointer addresses
the starting location of the active working register group.
Note: Registers E0-EF of Bank 0 are only accessed
through working registers and indirect addressing modes.
Stack. The Z86L7X internal register file is used for the
stack. An 8-bit Stack Pointer (R255) is used for the internal
stack that resides in the general-purpose registers (R4-
R239).
Zilog
r7 r6 r5 r4
r3 r2 r1 r0 _R253
The upper nibble of the register file address
provided by the register pointer specifies
the active working-register group
7F
70
6F
60
5F
50
4F
40
3F
Specified Working
Register Group
30
2F
The lower nibble
of the register
file address
provided by the
instruction points
to the specified
register
20
1F
Register Group 1
10
0F
Register Group 0
R15 to R0
R15 to R4 *
00
I/O Ports
R3 to R0 *
* RP = 00: Selects Register Group 0, Working Register 0.
Figure 16. Register Pointer
1-22
PRELIMINARY
DS97LVO0500