MPC563XM Reference Manual, Rev. 1
584
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
Figure 18-7. Platform RAM ECC Address (PREAR) Register
18.4.1.8
Platform RAM ECC Syndrome Register (PRESR)
The PRESR is an 8-bit register for capturing the error syndrome of the last, properly-enabled ECC event
in the platform RAM memory. Depending on the state of the ECC Configuration Register, an ECC event
in the platform RAM causes the address, attributes and data associated with the access to be loaded into
the PREAR, PRESR, PREMR, PREAT and PREDR registers, and the appropriate flag (PRNCE) in the
ECC Status Register to be asserted.
The z3 core on this device is a cacheless processor. In order to improve performance on 32-bit write
accesses, the RAM ECC is calculated on a 32-bit boundary versus the 64-bit organization used on
Copperhead and Moccasin. For the cacheless Z3 processor, most RAM writes will be 32 bits or smaller in
size. It was estimated that implementation of a 32-bit RAM ECC provides 7-8% overall performance
improvement over a 64-bit organization that would force read-modify-write cycles to write 32-bit data.
Each 32-bit word requires a 7-bit ECC code, so the RAM array is organized in two banks of 39 bits each.
In order to support the new 32-bit boundary ECC structure and maintain compatibility with other devices
of the eSys family, the device 7-bit syndrome and bank select (even, odd) were remapped into the
equivalent 8-bit syndrome of 64-bit organized memories (see
).
The PRESR register can only be read from the IPS programming model; any attempted write is ignored.
See
for the Platform RAM ECC Syndrome Register definition.
Register address: ECSM Base + 0x60
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
PREAR
W
RESET:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
PREAR
W
RESET:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
= Unimplemented
Table 18-8. Platform RAM ECC Address (PREAR) Field Descriptions
Name
Description
Value
PREAR
RAM ECC
Address
Register
This 32-bit register contains the faulting access address of the last,
properly-enabled platform RAM ECC event.