mc68hc912bc32 Freescale Semiconductor, Inc, mc68hc912bc32 Datasheet - Page 82

• Manufacturer Part Number: mc68hc912bc32
• Description: M68hc12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Operating Modes and Resource Mapping
Read: Anytime
Write: Once in normal modes; anytime in special modes
NDRF — Narrow Data Bus for Register-Following Map Bit
RFSTR1 and RFSTR0 — Register-Following Stretch Bits
EXSTR1 and EXSTR0 — External Access Stretch Bit 1 and Bit 0
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This bit enables a narrow bus feature for the 512-byte register-following map. In expanded narrow
(8-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 moves also.
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, these bits have
no meaning or effect. See
These bits determine the amount of clock stretch on accesses to the external address space. In
single-chip and peripheral modes, these bits have no meaning or effect.
1 = Register-following map space acts the same as an 8-bit external data bus.
0 = Register-following map space acts as a full 16-bit external data bus.
Reset states:
Single-chip
Expanded
Address: $0013
modes:
modes:
Read:
Write:
Figure 5-5. Miscellaneous Mapping Control Register (MISC)
Bit 7
0
0
0
Table 5-3. Register-Following Stretch Bit Function
RFSTR1 and RFSTR0
EXSTR1 and EXSTR0
Table
NDRF
Table 5-4. Expanded Stretch Bit Function
6
0
0
00
01
10
11
00
01
10
11
M68HC12B Family Data Sheet, Rev. 9.1
5-3.
RFSTR1
5
0
0
RFSTR0
4
0
0
EXSTR1
E Clocks Stretched
E Clocks Stretched
3
1
1
0
1
2
3
0
1
2
3
EXSTR0
2
1
1
MAPROM
1
0
1
Freescale Semiconductor
ROMON
Bit 0
0
1