Module Operation
390
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Level 2 RAM (L2RAMW) Module
8.2.2.2
Memory Scrubbing
To increase memory reliability, the L2RAMW has an optional "memory scrubbing" feature, which
automatically corrects single bit errors whenever they are detected during any RAM read. The reason for
performing this action is that if a single bit error occurs on the RAM, and no immediate action is taken to
correct it, it is possible that a nearby bit cell will be corrupted as well at some point. If this were to occur,
the two corrupted bits would result in a double-bit error that can no longer be corrected by the SECDED
algorithm.
Memory scrubbing can be enabled by setting the Memory Scrubbing Enable (MSE) bit in the L2RAMW
Module Control Register (RAMCTRL). Note that the ECC Detect Enable (ECC_DETECT_EN) field in
RAMCTRL must be set to Ah before enabling memory scrubbing, since memory scrubbing uses the
L2RAMW SECDED logic.
8.2.2.3
SECDED Malfunction
To enhance device safety, the L2RAMW has a SECDED malfunction detection feature to ensure that the
SECDED logic is functioning correctly. Every time ECC is calculated for a CPU write data or a read data
for a read-modify-write operation, the results of the ECC correction are compared back again to the
original data value to ensure that the SECDED logic is working correctly. If an error in the SECDED logic
is detected, it will be flagged in the RAMERRSTATUS Register (RAM Error Status).
8.2.2.4
L2RAMW Error Types and Responses
Table 8-1. L2RAMW Error Types
Error Source
Corresponding RAMERRSTATUS Bit
ESM Group
CPU Write ECC single error (correctable)
CPUWE (0)
Group 1
ECC double bit errors:
Group 3, bus error
Read-Modify-Write (RMW) ECC double bit error
RMWDE (7)
CPU Write ECC double bit error
CPUWDE (5)
Uncorrectable error Type A:
Group 3, bus error
Write SECDED malfunction error
WEME (3)
Redundant address decode error
ADE (2)
Read SECDED malfunction error
REME (1)
Uncorrectable error Type B:
Group 2
Memory scrubbing SECDED malfunction error
MSSM (18)
Memory scrubbing redundant address decode error MSRA (17)
Memory scrubbing address / control parity error
MSACP (16)
ECC single bit and double bit diagnostic errors
DRDE(22), DRSE(21), DWDE(20), DWSE(19)
Merged mux diagnostic error
MMDE (12)
Write SECDED malfunction diagnostic error
WEMDE (11)
Read SECDED malfunction diagnostic error
REMDE (10)
Write data merged mux error
MME (9)
Redundant address decode diagnostic error
ADDE (4)
Command parity error on idle
CPEOI (15)
Address / Control parity error
PACE(8)
Group 3, bus error
Level 2 RAM illegal address error
n/a
n/a (bus error only)
Memory initialization error
MIE (13)
n/a (bus error only)