CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
61
RAM Paging
4.2.3
STK_PP Register
The Stack Page Pointer Register (STK_PP) is used to set
the effective SRAM page for stack memory accesses in a
multi-SRAM page PSoC device.
Bits 2 to 0: Page Bits[2:0].
These bits have the potential
to affect two types of memory access.
The purpose of this register is to determine which SRAM
page the stack will be stored on. In the reset state, this regis-
ter's value will be 0x00 and the stack will therefore be in
SRAM Page 0. However, if the STK_PP register value is
changed, the next stack operation will occur on the SRAM
page indicated by the new STK_PP value. Therefore, the
value of this register should be set early in the program and
never be changed. If the program changes the STK_PP
value after the stack has grown, the program must ensure
that the STK_PP value is restored when needed.
Note that the impact that the STK_PP register has on the
stack is independent of the SRAM Paging bits in the CPU_F
register.
The second type of memory accesses that the STK_PP reg-
ister affects are indexed memory accesses when the
CPU_F[7:6] bits are set to 11b. In this mode, source indexed
and destination indexed memory accesses are directed to
the stack SRAM page, rather than the SRAM page indicated
by the IDX_PP register or SRAM Page 0.
For additional information, refer to the
4.2.4
IDX_PP Register
The Index Page Pointer Register (IDX_PP) is used to set
the effective SRAM page for indexed memory accesses in a
multi-SRAM page PSoC device.
Bits 2 to 0: Page Bits[2:0].
These bits allow instructions,
which use the source indexed and destination indexed
address modes, to operate on an SRAM page that is not
equal to the current SRAM page. However, the effect this
register has on indexed addressing modes is only enabled
when the CPU_F[7:6] is set to 10b.
When CPU_F[7:6] is set to 10b and an indexed memory
access is made, the access is directed to the SRAM page
indicated by the value of the IDX_PP register.
See the STK_PP register description for more information
on other indexed memory access modes.
For additional information, refer to the
4.2.5
MVR_PP Register
The MVI Read Page Pointer Register (MVR_PP) is used to
set the effective SRAM page for MVI read memory accesses
in a multi-SRAM page PSoC device.
Bits 2 to 0: Page Bits[2:0].
These bits are only used by
the MVI A, [expr] instruction, not to be confused with the
MVI [expr], A instruction covered by the MVW_PP register.
This instruction is considered a read because data is trans-
ferred from SRAM to the microprocessor's A register
(CPU_A).
When an MVI A, [expr] instruction is executed in a device
with more than one page of SRAM, the SRAM address that
is read by the instruction is determined by the value of the
least significant bits in this register. However, the pointer for
the MVI A, [expr] instruction is always located in the current
SRAM page. See the
PSoC Designer Assembly Language
User Guide
for more information on the MVI A, [expr]
instruction.
The function of this register and the MVI instructions are
independent of the SRAM Paging bits in the CPU_F register.
For additional information, refer to the
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
0,D1h
Page Bits[2:0]
RW : 00
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
0,D3h
Page Bits[2:0]
RW : 00
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
0,D4h
Page Bits[2:0]
RW : 00
Summary of Contents for CY8C28 series
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