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ROM base address register (i.e. the ROM must be based at $0000 if ROM_VLD is
asserted).
5.3.2 ROM Programming Model
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The configuration information in the ROM base address register (ROMBAR) controls the
ROM module operation. The ROMBAR is accessible in supervisor mode as control register
$C00 using the MOVEC instruction. All undefined bits are reserved and should always be
written as zero. A hardware reset clears only the valid bit if ROM_VLD is negated. If
ROM_VLD is asserted, ROMBAR is reset to $0121. This activates the ROM with a starting
address of $0000 and all address spaces, except the CPU space, are allowed. This is shown
below where the reset values in parenthesis are valid if ROM_VLD is asserted during a
reset.
BITS
31
16
FIELD
BA
RESET
-(0)
R/W
W
BITS
15
9
8
7
6
5
1
0
FIELD
BA
WP
-
AS
V
RESET
-(0)
-(1)
-
-
0(1)
R/W
W
W
-
W
W
NOTE: The reset values in parenthesis are valid if the ROM_VLD signal is asserted during reset.
ROM Base Address Register (ROMBAR)
Field Definitions:
5.3.2.1 BA: ROMBAR[31:9]—BASE ADDRESS.
Defines the base address for the ROM module address range. The number of valid base
address bits in this field is a function of the ROM size as shown in Table 5-9. The base
address is reset to $0 if ROM_VLD is asserted during reset.
Table 5-9. Valid ROM Base Address Bits
ROM SIZE
5-16
VALID BA BITS
512
BA[31:9]
1K
BA[31:10]
2K
BA[31:11]
4K
BA[31:12]
8K
BA[31:13]
16K
BA[31:14]
32K
BA[31:15]
ColdFire2/2M User’s Manual
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