Chapter 23 Memory Mapping Control (S12XMMCV2)
MC9S12XDP512 Data Sheet, Rev. 2.11
Freescale Semiconductor 889
23.3.2.3 Global Page Index Register (GPAGE)
Read: Anytime
Write: Anytime
The global page index register is used only 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 1-7).
CAUTION
XGATE write access to this register during an CPU access which makes use
of this register could lead to unexpected results.
Figure 23-7. GPAGE Address Mapping
Example 23-1. This example demonstrates usage of the GPAGE register
LDAADR EQU $5000 ;Initialize LDADDR to the value of $5000
MOVB #$14, GPAGE ;Initialize GPAGE register with the value of $14
GLDAA >LDAADR ;Load Accu A from the global address $14_5000
Address: 0x0010
76543210
R0 GP6 GP5 GP4 GP3 GP2 GP1 GP0
W
Reset 00000000
= Unimplemented or Reserved
Figure 23-6. Global Page Index Register (GPAGE)
Table 23-7. 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 64-kilobyte pages is
to be accessed.
Bit16 Bit 0Bit15Bit22
CPU Address [15:0]GPAGE Register [6:0]
Global Address [22:0]