Review of FlashLINK JTAG interface

[petemate]

Hi guys, I need JTAG access to some old hardware and found the original software for programming said hardware. Its an ST PSD4235G2V, in case anyone is wondering.

Anyway, the old software supports a FlashLINK JTAG interface, which is really simple to make. So I copied the design and would like your inputs on the few changes I have made.

There are two versions of the old design:

https://media.digikey.com/pdf/Data%20Sheets/ST%20Microelectronics%20PDFS/FL-101.pdf (from 2002)

http://www.manley.com.cn/web/admin_ml32/pic/down/200882917341835980.pdf (From 2003)

It looks as though they re-did the design in 2003, but forgot a few things: A 100pF capacitor on a line and they changed shorting DB13 to DB8 to DB13 to DB20 instead. I believe this is a mistake and I found a forum post elsewhere that mentions this as a mistake. So I added a solder bridge to fix this, in case its needed.

Anyawy, I made a few other changes that I'd like you guys to review.

• They use 74A240/74VHC240, which are inverting buffer/drivers for U1. Since I couldn't get those from JLCPCB, I decided to use 74HC244 instead. That is a non-inverting buffer/driver. I believe the two cascaded inverters to be equal to my non-inverting solution. Is that correct?
• They use DM54ALS05A or 74AC05 for all the inverters, which are open-collector inverters. Again, I couldn't get that, so I decided to use 74HC04, which are push-pull versions. To make them open-collector compatible, I added a PNP transistor on the output. Any issues with this? 
• They use the signal JEN to control whether or not U1 should enable the outputs. The signal is inverted twice and is again open-collector. Since I had a spare buffer in U1, I decided to use that to buffer JEN instead of the double inverter, as this saves me an IC. However, I ran into the same open-collector vs push-pull problem and added a PNP transistor.
• I used 33 ohm resistor networks instead of 47 ohm ones.

Please let me know if you spot anything else!


Thanks for your help!

[CJay]

Should also work for PSD103 which I have a need for, what software are you going to use?

[petemate]

Should also work for PSD103 which I have a need for, what software are you going to use?

PSDSoft Express. It is freely available from the ST web page. Only problem is that I have to run it in an windows xp virtual machine and that the JTAG thingie works on a parallel port. So i'd have to get a parallel port interface or install on an old computer(probably the latter).

It doesn't appear that PSDSoft express supports anything below PSD3xx, though. You're welcome to get a copy of the design when its done.