MPC555
/
MPC556
MEMORY CONTROLLER
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
10-32
10.8.6 Dual-Mapping Option Register
,
*It is recommended that this field would hold values that are the power of 2 minus 1 (e.g., - 2
3
- 1 = 7 [0b111]).
Table 10-9 DMBR Bit Descriptions
Bit(s)
Name
Description
0
—
Reserved
1:6
BA
Base address. The base address field is compared (along with the address type field) to the
address of the address bus to determine whether an address should be dual-mapped by one
of the memory banks controlled by the memory controller. These bits are used in conjunction
with the AM[11:16] bits in the OR.
Bit 10: is cleared at reset. That way, the default range for the dual mapping is 2 Mbytes. Note
that by setting this bit, the range becomes 4 Mbyte, which includes memory space beyond the
flash EEPROM memory.
7:9
—
Reserved
10:12
AT
Address type. This field can be used to specify that accesses involving the memory bank are
limited to a certain address space type. These bits are used in conjunction with the ATM bits
in the OR. The default value at reset is to map data only. For a full definition of address types,
refer to
.
13:27
—
Reserved
28:30
DMCS
Dual-mapping chip select. This field determines which chip-select pin is assigned for dual
mapping.
000 = CS[0]
001 = CS[1]
010 = CS[2]
011 = CS[3]
1xx = Reserved
31
DME
Dual mapping enabled. This bit indicates that the contents of the dual-mapping registers and
associated base and option registers are valid and enables the dual-mapping operation. The
default value at reset comes from the internal data bus that reflects the reset configuration
word. See
10.6 Dual Mapping of the Internal Flash EEPROM Array
for more information.
0 = Dual mapping is not active
1 = Dual mapping is active
DMOR
—
Dual-Mapping Option Register
0x2F C144
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
AM
*
RESERVED
ATM
RESERVED
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
LSB
31
RESERVED
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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