MPC555
/
MPC556
MEMORY CONTROLLER
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
10-30
10.8.4 Memory Controller Option Registers (OR0 – OR3)
,
*It is recommended that this field would hold values that are the power of 2 minus 1 (e.g., - 2
3
- 1 = 7 [0b111]).
OR0 – OR3
—
Memory Controller Option Registers 0 – 3
0x2F C104, C10C,
C114, C11C
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
AM*
HRESET:
(OR[1:3])
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
HRESET
(OR0)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
LSB
31
AM*
ATM
CSNT
ACS
EHTR
SCY
BSCY
TRLX
HRESET: (OR[1:3]):
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
HRESET
(OR0)
0
0
0
0
0
0
0
0
1
1
1
1
0
1
1
0
Table 10-8 OR0 – OR3 Bit Descriptions
Bit(s)
Name
Description
0:16
AM
Address mask. This field allows masking of any corresponding bits in the associated base regis-
ter. Masking the address bits independently allows external devices of different size address
ranges to be used. Any clear bit masks the corresponding address bit. Any set bit causes the
corresponding address bit to be used in comparison with the address pins. Address mask bits
can be set or cleared in any order in the field, allowing a resource to reside in more than one area
of the address map. This field can be read or written at anytime.
Following a system reset, the AM bits are reset in OR0.
17:19
ATM
Address type mask. This field masks selected address type bits, allowing more than one address
space type to be assigned to a chip-select. Any set bit causes the corresponding address type
code bits to be used as part of the address comparison. Any cleared bit masks the corresponding
address type code bit. Clear the ATM bits to ignore address type codes as part of the address
comparison. Note that the address type field uses only AT[0:2] and does not need AT[3] to define
the memory type space.
Following a system reset, the ATM bits are reset in OR0.
20
CSNT
Chip-select negation time. Following a system reset, the CSNT bit is reset in OR0.
0 = CS
/
WE are negated normally.
1 = CS
/
WE are negated a quarter of a clock earlier than normal
Following a system reset, the CSNT bit is reset in OR0.
21:22
ACS
Address to chip-select setup. Following a system reset, the ACS bits are reset in OR0.
00 = CS is asserted at the same time that the address lines are valid.
01 = Reserved
10 = CS is asserted a quarter of a clock after the address lines are valid.
11 = CS is asserted half a clock after the address lines are valid
Following a system reset, the ACS bits are reset in OR0.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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