Datasheet

M68HC12B Family Data Sheet, Rev. 9.1

Freescale Semiconductor 39

Chapter 2

2.1 Introduction

The register block can be mapped to any 2-Kbyte boundary within the standard 64-Kbyte address space

by manipulating bits REG15–REG11 in the register initialization register (INITRG). INITRG establishes

the upper five bits of the register block’s 16-bit address. The register block occupies the first 512 bytes of

the 2-Kbyte block.

Default addressing (after reset) is indicated in Figure 2-1. For additional information, refer to Chapter 5

Operating Modes and Resource Mapping.

NOTE

In expanded and peripheral modes, these registers are not in the map:

• Port A data register, PORTA

• Port B data register, PORTB

• Port A data direction register, DDRA

• Port B data direction register, DDRB

In peripheral mode or in expanded modes with the emulate port E bit (EME) set, these registers are not

in the map:

• Port E data register, PORTE

• Port E data direction register, DDRE

In peripheral mode, these registers are not in the map:

• Mode register, MODE

• Pullup control register, PUCR

• Reduced drive register, RDRIV