HCS12 datasheet(72/126 Pages) NXP

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Device User Guide — 9S12KT256DGV1/D V01.09

Freescale Semiconductor

Section 4 Modes of Operation

4.1 Overview

Eight possible modes determine the operating configuration of the MC9S12K-Family. Each mode has an

associated default memory map and external bus configuration controlled by a further pin.

Three low power modes exist for the device.

4.2 Chip Configuration Summary

The operating mode out of reset is determined by the states of the MODC, MODB, and MODA pins during

reset ((Table 4-1)). The MODC, MODB, and MODA bits in the MODE register show the current

operating mode and provide limited mode switching during operation. The states of the MODC, MODB,

and MODA pins are latched into these bits on the rising edge of the reset signal. The ROMCTL signal

allows the setting of the ROMON bit in the MISC register thus controlling whether the internal Flash is

visible in the memory map. ROMON = 1 mean the Flash is visible in the memory map. The state of the

ROMCTL pin is latched into the ROMON bit in the MISC register on the rising edge of the reset signal.

For further explanation on the modes refer to the HCS12 MEBI Block Guide.

Table 4-1 Mode Selection

BKGD =

MODC

PE6 =

MODB

PE5 =

MODA

PK7 =

ROMCTL

ROMON

Bit

Mode Description

Special Single Chip, BDM allowed and ACTIVE. BDM is

allowed in all other modes but a serial command is

required to make BDM active.

Emulation Expanded Narrow, BDM allowed

Special Test (Expanded Wide), BDM allowed

Emulation Expanded Wide, BDM allowed

Normal Single Chip, BDM allowed

Normal Expanded Narrow, BDM allowed

Peripheral; BDM allowed but bus operations would cause

bus conﬂicts (must not be used)

Normal Expanded Wide, BDM allowed

HCS12 Datasheet(PDF) 72 Page - NXP Semiconductors