XC866_07 Datasheet, PDF (25/116 Pages) Infineon Technologies AG – 8-Bit Single-Chip Microcontroller

XC866
Functional Description
3.2.2.2 Address Extension by Paging
Address extension is further performed at the module level by paging. With the address
extension by mapping, the XC866 has a 256-SFR address range. However, this is still
less than the total number of SFRs needed by the on-chip peripherals. To meet this
requirement, some peripherals have a built-in local address extension mechanism for
increasing the number of addressable SFRs. The extended address range is not directly
controlled by the CPU instruction itself, but is derived from bit field PAGE in the module
page register MOD_PAGE. Hence, the bit field PAGE must be programmed before
accessing the SFR of the target module. Each module may contain a different number
of pages and a different number of SFRs per page, depending on the specific
requirement. Besides setting the correct RMAP bit value to select the SFR area, the user
must also ensure that a valid PAGE is selected to target the desired SFR. A page inside
the extended address range can be selected as shown in Figure 9.
SFR Address
(from CPU)
MOD_PAGE.PAGE
rw
SFR Data
(to/from CPU)
PAGE 0
SFR0
SFR1
SFRx
PAGE 1
SFR0
SFR1
SFRy
Module
PAGE q
SFR0
SFR1
SFRz
Figure 9 Address Extension by Paging
Data Sheet
21
V1.2, 2007-10