MC912DG128A Motorola, MC912DG128A Datasheet - Page 77

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

MISC — Miscellaneous Mapping Control Register
Miscellaneous System Control Register
9-mapping
MOTOROLA
RESET:
RESET:
ROMTST
Bit 7
0
0
NDRF
6
0
0
CALL and RTC instructions have a special single wire mechanism to
read and write this register without using an address bus.
Additional mapping and external resource controls are available. To use
external resources the part must be operated in one of the expanded
modes.
Normal modes: write once; Special modes: write anytime. Read
anytime.
ROMTST — FLASH EEPROM Test mode
NDRF — Narrow Data Bus for Register-Following Map Space
In normal modes, this bit is forced to zero.
This bit enables a narrow bus feature for the 1K byte
Register-Following Map. This is useful for accessing 8-bit peripherals
and allows 8-bit and 16-bit external memory devices to be mixed in a
system. In Expanded Narrow (eight bit) modes, Single Chip Modes,
and Peripheral mode, this bit has no effect.
RFSTR1
0 = 16K window for Flash memory is located from $8000-$BFFF
1 = 32K window for Flash memory is located from $8000-$FFFF
0 = Makes Register-Following MAP space act as a full 16 bit data
1 = Makes the Register-Following MAP space act the same as an
5
0
0
bus.
8 bit only external data bus (data only goes through port A
externally).
RFSTR0
Resource Mapping
4
0
0
EXSTR1
3
1
1
EXSTR0
2
1
1
Miscellaneous System Control Register
ROMHM
1
0
0
MC68HC912DT128A Rev 2.0
ROMON
Bit 0
Resource Mapping
0
1
peripheral or
Exp mode
SC mode
Mode
$0013
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