MC68HC912BL16 Datasheet, PDF (30/128 Pages) Freescale Semiconductor, Inc – 16-Bit Microcontroller

Freescale Semiconductor, Inc.
MISC — Miscellaneous Mapping Control Register
$0013
Bit 7
6
5
4
3
2
1
Bit 0
0
NDRF RFSTR1 RFSTR0 EXSTR1 EXSTR0 MAPROM ROMON
RESET:
0
0
0
0
1
1
0
0
Ex. Modes
RESET:
0
0
0
0
1
1
1
1
Sing. Chip
This register can be read anytime. In normal modes MISC can be written once; in special modes it can
be written anytime.
NDRF — Narrow Data Bus for Register-Following Map
This bit enables a narrow bus feature for the 512-byte register-following map. In expanded narrow (eight
bit) modes, single-chip modes, and peripheral mode, NDRF has no effect. The register-following map
always begins at the byte following the 512-byte register map. If the registers are moved this space will
also move.
0 = Register-following map space acts as a full 16-bit data bus
1 = Register-following map space acts the same as an 8-bit external data bus
RFSTR1, RFSTR0 — Register-Following Stretch Bit 1 and Bit 0
These bits determine the amount of clock stretch on accesses to the 512-byte register-following map. It
is valid regardless of the state of the NDRF bit. In single-chip and peripheral modes this bit has no
meaning or effect.
Table 11 Register-Following Stretch-Bit Definition
Stretch Bit RFSTR1 Stretch Bit RFSTR0 E Clocks Stretched
0
0
0
0
1
1
1
0
2
1
1
3
EXSTR1, EXSTR0 — External Access Stretch Bit 1 and Bit 0
These bits determine the amount of clock stretch on accesses to the external address space. In single-
chip and peripheral modes this bit has no meaning or effect.
Table 12 Expanded Stretch-Bit Definition
Stretch Bit EXSTR1 Stretch Bit EXSTR0 E Clocks Stretched
0
0
0
0
1
1
1
0
2
1
1
3
MAPROM — Map Location of Flash EEPROM
This bit determines the location of the on-chip Flash EEPROM. In expanded modes it is reset to zero.
In single-chip modes it is reset to one. If ROMON is zero, this bit has no meaning or effect.
0 = Flash EEPROM is located from $4000 to $7FFF
1 = Flash EEPROM is located from $C000 to $FFFF
MC68HC912BL16
30
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