Memory Mapping Control (S12XMMCV4)
MC9S12XHY-Family Reference Manual, Rev. 1.01
Freescale Semiconductor
163
3.3.2.2
Global Page Index Register (GPAGE)
Read: Anytime
Write: Anytime
The global page index register is used to construct a 23 bit address in the global map format. It is only used
when the CPU is executing a global instruction (GLDAA, GLDAB, GLDD, GLDS, GLDX,
GLDY,GSTAA, GSTAB, GSTD, GSTS, GSTX, GSTY) (see CPU Block Guide). The generated global
address is the result of concatenation of the CPU local address [15:0] with the GPAGE register [22:16] (see
Figure 3-7
).
Figure 3-7. GPAGE Address Mapping
Example 3-1. This example demonstrates usage of the GPAGE register
LDX
#0x5000
;Set GPAGE offset to the value of 0x5000
MOVB
#0x14, GPAGE
;Initialize GPAGE register with the value of 0x14
GLDAA
X
;Load Accu A from the global address 0x14_5000
Address: 0x0010
7
6
5
4
3
2
1
0
R
0
GP6
GP5
GP4
GP3
GP2
GP1
GP0
W
Reset
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 3-6. Global Page Index Register (GPAGE)
Table 3-4. GPAGE Field Descriptions
Field
Description
6–0
GP[6:0]
Global Page Index Bits 6–0 — These page index bits are used to select which of the 128 64KB pages is to be
accessed.
Bit16
Bit 0
Bit15
Bit22
CPU Address [15:0]
GPAGE Register [6:0]
Global Address [22:0]
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