Flash failure for batch of STR731
We have a bit of an issue with a batch of STR731FV2T7 microcontrollers (oldschool, I know) not being able to be flashed properly. Any help would be appreciated. We've verified all the usual suspects are not a problem (signal integrity, crystal oscillation, power supply rails all OK). We've also x-ray inspected the packages and the dies, bond wire and package all look the same as known working batches.
Anyway, when we try to flash the board with a SEGGER Flasher, we get the following:
SEGGER J-Link Commander V6.44h (Compiled May 3 2019 17:37:48)
DLL version V6.44h, compiled May 3 2019 17:37:09
Connecting to J-Link via USB...O.K.
Firmware: J-Link ARM / Flasher ARM V4 compiled Apr 18 2019 16:17:53
Hardware version: V4.02
S/N: 164215152
License(s): JFlash, GDB
IP-Addr: 10.0.0.156 (DHCP)
VTref=5.019V
Type "connect" to establish a target connection, '?' for help
J-Link>Please specify device / core. <Default>: STR731FV2
Type '?' for selection dialog
Device>Please specify target interface:
J) JTAG (Default)
TIF>Device position in JTAG chain (IRPre,DRPre) <Default>: -1,-1 => Auto-detect
JTAGConf>Specify target interface speed [kHz]. <Default>: 4000 kHz
Speed>Device "STR731FV2" selected.
Connecting to target via JTAG
Could not measure total IR len. TDO is constant high.
Could not measure total IR len. TDO is constant high.
Could not measure total IR len. TDO is constant high.
Could not measure total IR len. TDO is constant high.
Cannot connect to target.
I can get the emulator to recognise the microcontroller by either holding it in reset (pulling RST low), or by changing the boot mode to system memory, but in both cases the emulator can't flash or erase anything because it can't halt the CPU:
SEGGER J-Link Commander V6.44h (Compiled May 3 2019 17:37:48)
DLL version V6.44h, compiled May 3 2019 17:37:09
Connecting to J-Link via USB...O.K.
Firmware: J-Link ARM / Flasher ARM V4 compiled Apr 18 2019 16:17:53
Hardware version: V4.02
S/N: 164215152
License(s): JFlash, GDB
IP-Addr: 10.0.0.156 (DHCP)
VTref=5.024V
Type "connect" to establish a target connection, '?' for help
J-Link>Please specify device / core. <Default>: STR731FV2
Type '?' for selection dialog
Device>Please specify target interface:
J) JTAG (Default)
TIF>Device position in JTAG chain (IRPre,DRPre) <Default>: -1,-1 => Auto-detect
JTAGConf>Specify target interface speed [kHz]. <Default>: 4000 kHz
Speed>Device "STR731FV2" selected.
Connecting to target via JTAG
TotalIRLen = 4, IRPrint = 0x01
JTAG chain detection found 1 devices:
#0 Id: 0x3F0F0F0F, IRLen: 04, ARM7TDMI Core
ARM7 identified.
J-Link>Using DBGRQ to halt CPU
Resetting TRST in order to halt CPU
****** Error: Unable to halt CPU core
Downloading file [C:\firmware\binaries\20200423.hex]...
****** Error: Failed to download RAMCode.
Failed to prepare for programming.
Failed to download RAMCode!
Can not read register 0 (R0) while CPU is running
Can not read register 1 (R1) while CPU is running
Can not read register 2 (R2) while CPU is running
Can not read register 3 (R3) while CPU is running
Can not read register 4 (R4) while CPU is running
Can not read register 5 (R5) while CPU is running
Can not read register 6 (R6) while CPU is running
Can not read register 7 (R7) while CPU is running
Can not read register 10 (R8_USR) while CPU is running
Can not read register 11 (R9_USR) while CPU is running
Can not read register 12 (R10_USR) while CPU is running
Can not read register 13 (R11_USR) while CPU is running
Can not read register 14 (R12_USR) while CPU is running
Can not read register 15 (R13_USR) while CPU is running
Can not read register 16 (R14_USR) while CPU is running
Can not read register 9 (R15 (PC)) while CPU is running
Can not read register 8 (CPSR) while CPU is running
Can not read register 30 (R14_ABT)
Unspecified error -1
J-Link>
Changing JTAG clock speeds doesn't help, either.
Any ideas? The package markings on the IC show:
STR731FV2T7
Y
22 3VT VG
MLT 22 748