There is no/TRST pin on 56F8247. You can leave the /TRST open on the JTAG interface with USBTAP.
Please connect the RESET signal on the JTAG interface with GPIOD4/RESET pin on 56F8257.
You may refer to the schematic of our 56F8257 demo board:
http://cache.freescale.com/files/microcontrollers/hardware_tools/schematics/TWR-56F8257-SCH_B.pdf
Do you have a DSC demo or EVM board? To confirm this is not a software or driver problem.
Fiona Kuang
Technical Information & Commercial Support
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