Z86D86 Datasheet, PDF (41/80 Pages) Zilog, Inc. – 28-Pin Low-Voltage OTP Microcontroller

Z86D86
28-Pin Low-Voltage OTP Microcontroller
33
r₇ ^r₆ r₅ r₄
r₃ r₂ r₁ r_{0 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
30
Register Group
2F
20
1F
Register Group 1
10
0F
Register Group 2
00
I/O Ports
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*
* RP =00: Selects Register Group 0, Working Register 0
Figure 31. Register Pointer
Stack
The Z86D86 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). SPH is used as a general-purpose register only when using internal
stacks.
Note: When SPH is used as a general-purpose register and Port 0 is
in address mode, the contents of SPH are loaded into Port 0
whenever the internal stack is accessed.
PS008905-0105
PRELIMINARY