More on the pluto-p (including FPGA pin numbers for the "JTAG" connector

There are a lot of questions about the pluto-p that are left unanswered by the website and the "getting started" document to which you're given a link to after you order. I've tried to answer them for myself, and now I'm sharing those answers with my readers. The most important thing I report here is the ACEX pin numbers for the JTAG connector.

The "JTAG" connector

The "JTAG" connector is not connected to the JTAG pins of the ACEX, but is instead connected to GPIOs through 22-ohm current-limiting resistors. However, the "getting started" document does not give the ACEX pin numbers. They are:
93 GND
(key) 5 9
10 13
16 GND

Other doodads on the board

On the underside, there's a 40MHz oscillator, a 3.3V regulator (1117-3.3, a low-dropout type), a bunch of bypass capacitors, and a few interesting bits with transistors.

Two of the parts I've decyphered already: they're one-transistor inverters for pins 11 and 12 of the parallel port, which the "Getting started with Pluto-P" PDF file shows are inverted. I think this is because the ACEX's outputs have weak pull-ups prior to configuration, but these pins must read as GND by the PC for the "configure by printing to it" to work.

There's a third transistor whose use I haven't yet found. It is marked "G1", appears to be a BFS20 NPN transistor with the base connected to nStatus and the collector connected to one of the VCC_io pins (pin 44). However, I'm not entirely sure about this, and I can't figure out what good it would do. (is this what causes the LED to glow dimly when the device is not yet programmed?)

The DC adapter

The DC adapter is rated "9V DC 300mA", but the no-load voltage from the adapter is +15V. The getting started document says that the input may be "between +5V and +10V". The onboard 3.3V DC regulator does get somewhat warm, but not too warm to touch for extended periods of time.

Entry first conceived on 2 December 2006, 17:43 UTC, last modified on 15 January 2012, 3:46 UTC
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