mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 72

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 1 MC9S12E256 Device Overview (MC9S12E256DGV1)
1.6
1.6.1
Eight possible modes determine the operating configuration of the MC9S12E256. 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.
1.6.2
The operating mode out of reset is determined by the states of the MODC, MODB, and MODA pins during
reset. 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
(MEBIV3)”.
72
BKGD =
MODC
0
0
0
0
1
1
1
1
Modes of Operation
Overview
Chip Configuration Summary
MODB
PE6 =
0
0
1
1
0
0
1
1
PE7 = XCLKS
MODA
PE5 =
0
1
0
1
0
1
0
1
1
0
Table 1-8. Clock Selection Based on PE7
ROMCTL
PK7 =
MC9S12E256 Data Sheet, Rev. 1.08
X
X
X
X
Colpitts Oscillator selected
Pierce Oscillator/external clock selected
0
1
0
1
0
1
0
1
Table 1-7. Mode Selection
Chapter 18, “Multiplexed External Bus Interface
ROMON
Bit
1
1
0
0
1
0
1
0
1
1
0
1
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
Mode Description
Freescale Semiconductor