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Great. I haven't tried accessing a USB-Blaster under windows.
Write some test code;
a) Toggle TCK, while keeping all other bits high, so according to the protocol:
0011_1111 b /* bit mode, don't read-back, OE + TDI + CS# + CE# + TCK high */
0011_1110 b /* drop TCK low */
So fill a write buffer with 3-bytes, i.e., 3Fh, 3Eh, 3Fh, and write it to the USB-Blaster.
Probe the TCK pin and you will see a ~1us low pulse on TCK.
Viola, you now have control of your USB-Blaster!
Cheers,
Dave
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Well yes and no .....
I have for a USB Blaster JTAG connector connected to the JTAG connectore on Morphic II,
being the easiest for me to test :
Orientation : Pins 2, 10 : Gnd
Pin 4 : Vcc
Then the JTAG connectors are bought out to Morhic IO connectors :
Morphic II 0.1" connectors Altera USB Blaster (JTAG Mode)
J3-23 JTAG_TDI JTAG Interface Pin 9
J3-24 JTAG_TMS JTAG Interface Pin 5
J4-23 JTAG_TDO JTAG Interface Pin 3
J4-24 JTAG_TCK JTAG Interface Pin 1
If Toggle Toggling
Bit 0 TDI Pin 9, TMS Pin 5
If I write the 3Fh, 3Eh, 3Fh to the USB Blaster (and then call a Tx purge)
Or as decimal and binary :
63 62 63
0 0 1 1 1 1 1 1
0 0 1 1 1 1 1 0
0 0 1 1 1 1 1 1
Then I have toggling : TDI Pin 9, TMS Pin 5,
with TCK and TDO low.
This is indeed a 1us low pulse.
In fact it does not seem to matter which bit I toggle (other than the far left one),
I get the same behaviour.
Puzzled.
Honored Contributor
