MPC555
/
MPC556
STATIC RANDOM ACCESS MEMORY (SRAM)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
20-3
20.3.2 SRAM Test Register (SRAMTST)
SRAMTST — SRAM Test Register
0x38 0004, 0x38 000C
The SRAM test register is used for factory testing only.
SRAMMCR —
SRAM Module Configuration Register
0x38 0000
0x38 0008
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
LCK
DIS
2CY
RESERVED
RESET:
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
RESERVED
R0
D0
S0
R1
D1
S1
R2
D2
S2
R3
D3
S3
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Table 20-1 SRAMMCR Bit Descriptions
Bit(s)
Name
Description
0
LCK
Lock bit. This bit can be set only once and cleared only by reset.
0 = Writes to the SRAMMCR are accepted
1 = Writes to the SRAMMCR are ignored
1
DIS
Module disable
0 = SRAM module is enabled
1 = SRAM module is disabled. Module can be subsequently re-enabled by software set-
ting this bit or by reset. Attempts to read SRAM array when it is disabled result in
internal TEA assertion.
2
2CY
Two-cycle mode
0 = SRAM module is in single-cycle mode (normal operation)
1 = SRAM module is in two-cycle mode. In this mode, the first cycle is used for decoding
the address, and the second cycle is used for accepting or providing data. This
mode provides some power savings while keeping the memory active.
3:19
—
Reserved
20, 23, 26,
29
Rx
(x = 0, 1, 2, 3)
Read only. R0 controls the highest 4-Kbyte block (lowest address) of the SRAM array;
R3 controls the lowest block (highest address).
0 = 4-Kbyte block is readable and writable
1 = 4-Kbyte block is read only. Attempts to write to this space result in internal TEA as-
sertion.
21, 24, 27,
30
Dx
(x = 0, 1, 2, 3)
Data only. D0 controls the highest 4-Kbyte block (lowest address) of the SRAM array; D3
controls the lowest block (highest address).
0 = 4-Kbyte block can contain data or instructions
1 = 4-Kbyte block contains data only. Attempts to load instructions from this space result
in internal TEA assertion.
22, 25, 28,
31
Sx
(x = 0, 1, 2, 3)
Supervisor only. S0 controls the highest 4-Kbyte block (lowest address) of the SRAM ar-
ray; S3 controls the lowest block (highest address).
0 = 4-Kbyte block is placed in unrestricted space
1 = 4-Kbyte block is placed in supervisor space. Attempts to access this space from the
user privilege level result in internal TEA assertion.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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