I found this site ( https://github.com/dwelch67/raspberrypi ... er/armjtag ) with bare metal examples and an ARM JTAG sample, which says that the TMS pin comes from S5 pin 11. The only problem is, I don't know which pin on S5 is 11 – which one is pin 1? and which way does the numbering go?
Also, just to make sure I'm not completely off, S5 is the 30-pin connector between the HDMI and Ethernet ports, correct?
(I gather all this would be much simpler if I had a rev 2.0 board, but sadly I was an early adopter )