MC9S12DT128 Datasheet, PDF (77/142 Pages) Freescale Semiconductor, Inc – Device User Guide

Device User Guide — 9S12DT128DGV2/D V02.15
Section 4 Modes of Operation
4.1 Overview
Eight possible modes determine the operating configuration of the MC9S12DT128. 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.
BKGD = PE6 =
MODC MODB
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
PE5 =
MODA
0
1
0
1
0
1
0
1
Table 4-1 Mode Selection
PK7 =
ROMCTL
X
0
1
X
0
1
X
0
1
X
0
1
ROMON
Bit
1
1
0
0
1
0
1
0
1
1
0
1
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
Special Peripheral; BDM allowed but bus operations
would cause bus conflicts (must not be used)
Normal Expanded Wide, BDM allowed
For further explanation on the modes refer to the HCS12 Multiplexed External Bus Interface Block Guide.
Table 4-2 Clock Selection Based on PE7
PE7 = XCLKS
Description
1
Colpitts Oscillator selected
0
Pierce Oscillator/external clock selected
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