MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor
8-1
Chapter 8
Error Correction Status Module (ECSM)
8.1
Introduction
The MPC5553/MPC5554 includes error-correcting code (ECC) implementations to improve the quality
and reliability of internal SRAM and internal flash memories. The error correction status module (ECSM),
provides a means for the application to collect information on memory errors reported by ECC and/or
generic access error information.
8.1.1
Overview
The ECSM provides a set of registers that configure and report ECC errors for the MPC5553/MPC5554
device including accesses to SRAM and flash memory. The application may configure the device for the
types of memory errors to be reported, and then query a set of read-only status and information registers
to identify any errors that have been signalled.
There are two types of ECC errors: correctable and non-correctable. A correctable ECC error is generated
when only one bit is wrong in a 64-bit doubleword. In this case it is corrected automatically by hardware,
and no flags or other indication is set that the error occurred. A non-correctable ECC error is generated
when 2 bits in a 64-bit doubleword are incorrect. Non-correctable ECC errors cause an interrupt, and if
enabled, additional error details are available in the ECSM.
Error correction is implemented on 64 bits of data at a time, using 8 bits for ECC for every 64-bit
doubleword. ECC is checked on reads, and calculated on writes per the following:
1. 64 bits containing the desired byte / halfword / word or doubleword in memory is read, and ECC
checked.
2. If the access is a write, then
— The new byte / halfword / word / doubleword is merged into the 64 bits.
— New ECC bits are calculated.
— The 64 bits and the new ECC bits are written back.
In order to use ECC with SRAM, the SRAM memory must be written to before ECC is enabled. See
Section 15.7, “Initialization/Application Information
.”
8.1.2
Features
The ECSM includes these features:
•
Configurable for reporting non-correctable errors
•
Registers for capturing ECC information for RAM access errors
•
Registers for capturing ECC information for flash access errors
Summary of Contents for MPC5553
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