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ST90158 - DEVICE ARCHITECTURE
SYSTEM REGISTERS
(Cont’d)
POINTER 0 REGISTER (RP0)
R232 - Read/Write
Register Group: E (System)
Reset Value: xxxx xx00 (xxh)
Bits 7:3 =
RG[4:0]
:
Register Group number.
These bits contain the number (in the range 0 to
31) of the register block specified in the
srp0
or
srp
instructions. In single 16-register mode the
number indicates the lower of the two 8-register
blocks to which the 16 working registers are to be
mapped, while in twin 8-register mode it indicates
the 8-register block to which
r0
to
r7
are to be
mapped.
Bit 2 =
RPS
:
Register Pointer Selector
.
This bit is set by the instructions
srp0
and
srp1
to
indicate that the twin register pointing mode is se-
lected. The bit is reset by the
srp
instruction to in-
dicate that the single register pointing mode is se-
lected.
0: Single register pointing mode
1: Twin register pointing mode
Bits 1:0: Reserved. Forced by hardware to zero.
POINTER 1 REGISTER
(RP1)
R233 - Read/Write
Register Group: E (System)
Reset Value: xxxx xx00 (xxh)
This register is only used in the twin register point-
ing mode. When using the single register pointing
mode, or when using only one of the twin register
groups, the RP1 register must be considered as
RESERVED and may NOT be used as a general
purpose register.
Bits 7:3 =
RG[4:0]:
Register Group number.
These bits contain the number (in the range 0 to
31) of the 8-register block specified in the
srp1
in-
struction, to which
r8
to
r15
are to be mapped.
Bit 2 =
RPS
:
Register Pointer Selector
.
This bit is set by the
srp0
and
srp1
instructions to
indicate that the twin register pointing mode is se-
lected. The bit is reset by the
srp
instruction to in-
dicate that the single register pointing mode is se-
lected.
0: Single register pointing mode
1: Twin register pointing mode
Bits 1:0: Reserved. Forced by hardware to zero.
7
0
RG4
RG3
RG2
RG1
RG0
RPS
0
0
7
0
RG4
RG3
RG2
RG1
RG0
RPS
0
0
9