The Olimex ARM JTAG clone is well known as there are many schematics in the internet available. Circuits is very simple and seems to be reliable. This adapter can be also set up to work with WinARM tools: ocdremote and gdb/Insight-gdb.

In the circuit there is a critical part that needs to be considered – 74HC244 buffer IC. Family of HC support less than 4.8V if powered with 3.3V. But reality shows that Parallel port voltage usually is lower than 5V, so HC will fit. But of course it is better to measure the HIGH state of parallel port pins.

To be more sure HC should be replaced by 74LVP244 or 74LPT244. These chips support 5.5V in entry with 3.3V supply but sometimes they are hard to find in the market.

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