Datasheet

Chapter 19 Module Mapping Control (MMCV4)
MC9S12E128 Data Sheet, Rev. 1.07
550 Freescale Semiconductor
19.3.2.4 Miscellaneous System Control Register (MISC)
Read: Anytime
Write: As stated in each bit description
NOTE
Writes to this register take one cycle to go into effect.
This register initializes miscellaneous control functions.
76543210
R0000
EXSTR1 EXSTR0 ROMHM ROMON
W
Reset: Expanded
or Emulation
0000110—
1
Reset: Peripheral
or Single Chip
00001101
Reset: Special Test 00001100
1. The reset state of this bit is determined at the chip integration level.
= Unimplemented or Reserved
Figure 19-6. Miscellaneous System Control Register (MISC)
Table 19-5. INITEE Field Descriptions
Field Description
3:2
EXSTR[1:0]
External Access Stretch Bits 1 and 0
Write: once in normal and emulation modes and anytime in special modes
This two-bit field determines the amount of clock stretch on accesses to the external address space as shown in
Table 19-6. In single chip and peripheral modes these bits have no meaning or effect.
1
ROMHM
FLASH EEPROM or ROM Only in Second Half of Memory Map
Write: once in normal and emulation modes and anytime in special modes
0 The fixed page(s) of FLASH EEPROM or ROM in the lower half of the memory map can be accessed.
1 Disables direct access to the FLASH EEPROM or ROM in the lower half of the memory map. These physical
locations of the FLASH EEPROM or ROM remain accessible through the program page window.
0
ROMON
ROMON — Enable FLASH EEPROM or ROM
Write: once in normal and emulation modes and anytime in special modes
This bit is used to enable the FLASH EEPROM or ROM memory in the memory map.
0 Disables the FLASH EEPROM or ROM from the memory map.
1 Enables the FLASH EEPROM or ROM in the memory map.
Table 19-6. External Stretch Bit Definition
Stretch Bit EXSTR1 Stretch Bit EXSTR0 Number of E Clocks Stretched
00 0
01 1
10 2
11 3