Z86D86 Datasheet, PDF (40/80 Pages) Zilog, Inc. – 28-Pin Low-Voltage OTP Microcontroller

Z86D86
28-Pin Low-Voltage OTP Microcontroller
32
R253 RP
D7 D6 D5 D4 D3 D2 D1 D0
Default setting after
reset = 0000 0000
Expanded Register Bank
Pointer
Working Register
Pointer
Figure 28. Register Pointer—FDH: Read/Write
R254 SPH
D7 D6 D5 D4 D3 D2 D1 D0
General Purpose Register
Byte (SP15–SP8)
Figure 29. Stack Pointer High—FEH: Read/Write
R255 SPL
D7 D6 D5 D4 D3 D2 D1 D0
Stack Pointer Lower
Byte (SP7–SP0)
Figure 30. Stack Pointer Low—FFH: Read/Write
Register File
The register file (bank 0) consists of four I/O port registers, 237 general-purpose
registers, and 16 control and status registers (R0–R3, R4–R239, and R240–255,
respectively). Additional, there are two expanded registers groups in Banks D and
F. Instructions can access registers directly or indirectly through an 8-bit address
field, thereby allowing a short, 4-bit register address to use the Register Pointer
(Figure 31). 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: Working register group E0–EF can only be accessed through
working registers and indirect addressing modes.
PS008905-0105
PRELIMINARY