PC912XDP512F0MPVR datasheet(666/1348 Pages) FREESCALE

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Chapter 18 Memory Mapping Control (S12XMMCV3)

MC9S12XDP512 Data Sheet, Rev. 2.21

666

Freescale Semiconductor

18.3.2.7

EEPROM Page Index Register (EPAGE)

Read: Anytime

Write: Anytime

These eight index bits are used to page 1 KByte blocks into the EEPROM page window located in the local

(CPU or BDM) memory map from address 0x0800 to address 0x0BFF (see Figure 18-14). This supports

accessing up to 256 Kbytes of EEPROM (in the Global map) within the 64 KByte Local map. The

EEPROM page index register is effectively used to construct paged EEPROM addresses in the Local map

format.

CAUTION

XGATE write access to this register during an CPU access which makes use

of this register could lead to unexpected results.

Figure 18-14. EPAGE Address Mapping

The reset value of 0xFE ensures that there is a linear EEPROM space available between addresses 0x0800

and 0x0FFF out of reset.

The ﬁxed 1K page 0x0C00–0x0FFF of EEPROM is equivalent to page 255 (page number 0xFF).

Address: 0x0017

76543210

EP7

EP6

EP5

EP4

EP3

EP2

EP1

EP0

Reset

11111110

Figure 18-13. EEPROM Page Index Register (EPAGE)

Table 18-13. EPAGE Field Descriptions

Field

Description

7–0

EP[7:0]

EEPROM Page Index Bits 7–0 — These page index bits are used to select which of the 256 EEPROM array

pages is to be accessed in the EEPROM Page Window.

Bit16

Bit0

Bit9

Address [9:0]

EPAGE Register [7:0]

Global Address [22:0]

Bit10

Bit17

Address: CPU Local Address

or BDM Local Address

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