Overview
1735
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
eFuse Controller
32.1 Overview
Electrically programmable fuses (eFuses) are used to configure the device after deassertion of PORRST.
The eFuse values are read and loaded into internal registers as part of the power-on-reset sequence. The
eFuse values are protected with single bit error correction, double bit error detection (SECDED) codes.
These fuses are programmed during the initial factory test of the device. The eFuse controller is designed
so that the state of the eFuses cannot be changed once the device is packaged.
32.2 Introduction
The eFuse controller automatically reads the values of the eFuses and shifts them into registers during the
power-on reset sequence. No action is required from the application code. However, in a safety critical
application, the user code should check to see if a correctable or an uncorrectable error was detected
during the reset sequence and then preform a self-test on the eFuse controller ECC logic.
32.3 eFuse Controller Testing
32.3.1 eFuse Controller Connections to ESM
There are three connections from the eFuse controller to the Error Signaling Module (ESM). If an
uncorrectable error occurs during the loading of the eFuse values after reset, a group three, channel one
error and a group one channel 40 error are sent to the ESM. The group three error will cause the ERROR
pin to go low. If during the eFuse loading a correctable error occurs, only a group one channel 40 error is
sent to the ESM. If an error occurs during the eFuse controller self test, then a group one channel 41 error
and a group one channel 40 error are sent to the ESM. After reset, by default, the group one errors do not
affect the ERROR pin. If the software enables the appropriate bit in the appropriate ESM Influence Error
Pin Set/Status Register (ESMIEPSRn) while the group one error is set, the ERROR pin will go low.
Table 32-1. ESM Signals Set by eFuse Controller
ESM Signal
Uncorrected Load
Failure
Correctable Load
Error
Self Test
eFuse Self Test
eFuse stuck at 0 Test
Version a:
with Error pin
Version b:
without Error pin
Group 3 Channel 1
X
X
Group 1 Channel 40
X
X
X
Group 1 Channel 41
X
X
X
32.3.2 Checking for eFuse Errors After Power Up
For safety critical systems, it is required that you check the status of the eFuse controller after a device
reset. A suggested flow chart for checking the eFuse controller after device reset is shown in
.
Failures during the eFuse self test can be grouped into three levels of severity. Depending on the safety
critical application, the error handling for each error type may be different.
32.3.2.1 Class 1 Error
A class 1 error of the eFuse controller means that there was a failure during the autoload sequence. The
values read from the eFuses cannot be relied on. All device operation is suspect. A class 1 error is
indicated by a signal to group 3 channel 1 of the ESM. This will cause the ERROR pin to go active low.
32.3.2.2 Class 2 Errors
A class 2 error is an indication that the safety checks of the eFuse controller did not work. These are also
serious errors because you can no longer guarantee that a more severe error did not occur.
