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Question: Why does device init, connect, or programming fail?
Answer: Frequently the cause is a bad connection between the MSP-GANG Programmer and the target device. A 14-wire ribbon cable is provided for JTAG/SBW or BSL connection between MSP-GANG and target device. The ribbon cable has an impedance of approximately 100 Ω and has DC lines in the ribbon cable to provide good isolation between signal wires (TDI, TCK, TMS, TDO). Each signal wire is separated by a DC wire to minimize crosstalk between the signal wires. The following pinout used in the MSP-GANG on each JTAG connector:
1 - TDO (Signal wire)
2 - Vcc / Vcc sense (DC wire)
3 - TDI (Signal wire)
4 - Vcc sense (DC wire)
5 - TMS (Signal wire)
6 - n/c (DC wire)
7 - TCK (Signal wire)
8 - TEST (DC wire in JTAG)
9 - GND (DC wire)
10 - n/c (DC wire)
11 - RESET (DC wire in JTAG)
12 - BSL-Tx (Signal wire)
13 - n/c (DC wire)
14 - BSL-Rx (Signal wire)
The provided 14-pin connector might not be ideal for some customers who want to minimize the number of wires and pinout order. When using a custom cable, make sure to address the issue of crosstalk between signal cables. Unfortunately, in many cases the custom cable does not provide good isolation between signal wires. As an example of a bad connection, the following uses an 8-wire ribbon cable for JTAG communication:
1 - Vcc / Vcc sense (DC wire)
2 - TDO (Signal wire)
3 - TDI (Signal wire)
4 - TMS (Signal wire)
5 - TCK (Signal wire)
6 - TEST (DC wire in JTAG)
7 - GND (DC wire)
8 - RESET (DC wire in JTAG)
On this connection, the TMS signal is coupled with the TCK and TDI lines and can generate additional TCK pulses on the TCK wire (rise time on TMS line can be seen on the TCK line also and can be detected by the MSP MCU as an additional unexpected TCK pulse).
