2013-01-08 02:14 PM
Does the so-called ''JTAG fuse'' prevent me from using boundary scan to toggle IOs?
DP #rtfm #jtag-fuse-ip-read-protection2013-01-09 02:19 AM
STM32 has no Fuses. However Code can configure the Pins used for JTAG/SWD for other uses, resulting no JTAG/SWD access after the code configuring the pins has been executed.
2013-01-09 04:42 AM
It has options bytes, which have an equivalent function.
From PM0059�? Level 2: Disable debug/chip read protectionWhen the read protection Level 2 is activated by writing 0xCC to the RDP option byte,
all protections provided by Level 1 are active, system memory and all debug features
(CPU JTAG and single-wire) are disabled when booting from SRAM or from system
memory, and user options can no longer be changed.
Memory read protection Level 2 is an irreversible operation. When Level 2 is activated,
the level of protection cannot be decreased to Level 0 or Level 1.
Note: The JTAG port is permanently disabled when Level 2 is active (acting as a JTAG fuse). As a consequence, boundary scan cannot be performed. STMicroelectronics is not able to perform analysis on defective parts on which the Level 2 protection has been set.
Do your boundary scan and testing BEFORE programming the device. Place raw unprogrammed devices, or where you can programmatically enable RDP via the application or boot loader.