Z86L81 Datasheet, PDF (33/88 Pages) Maxim Integrated Products – 28-Pin Low-Voltage Infrared Microcontrollers

Z86L81/86/98
28-Pin Low-Voltage Infrared Microcontrollers
27
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
30
{ 2F
20
{ 1F
10
{ 0F
00
Specified Working
Register Group
Register Group 1
Register Group 0
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 13. Register Pointer—Detail
Note: Working register group E0–EF can only be accessed through
working registers and indirect addressing modes.
Stack
The Z86L81/86/98 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.
19-4615; Rev 0; 4/09