I have used my GQ-4X for a few years without any problems on a range of EPROMs.
Now I would like to program a few 2716 EPROMS. The programming fails on the first byte.
I have external 9V power supply connected to the GQ-4X.
During programming of a AMD AM2716 I monitored VPP and PGM (programming pulse) with an oscilloscope. Both are wrong.
According to the datasheet the PGM (programming pulse) should have a duration of about 50 ms (MIN: 45 ms and MAX 55 ms). The actual programming pulse varies between about 100 us and 2 ms, so is MUCH too short. Trying to change the Speed parameter from the default +2 to 0 and -2 makes no difference for the pulse width, but increases the interval between the pulses.
VPP without an EPROM inserted is about 27V (2V too high), but with an EPROM inserted it drops VPP to only about 11V. It should be about 25V, but never more than 26V.
I have bent the VPP pin up to be able to measure the actual VPP current and it is only 18 mA. The datasheet specifies for the VPP current a MAX of 30 mA. So the part is well within specification.
I have tried with AMD AM2716 and NS M2716Q both fail in the same way.
The programmer reliably programs M2732A-20F1 made by ST. Of course VPP is on a different pin and the device family is different so the programming pulses are probably within spec (I haven't checked this).
So it appears I have two problems:
1) a software or firmware bug where the programming pulse is much too short (and varies by more than a magnitude).
2) a possible hardware problem with the circuit being unable to sustain VPP under load (18 mA) on the 2716 pin 21.
I have now tried with M2716F1 EPROMs made by ST and they work perfectly every time. They require a 21V VPP.
As to the two problems I described above:
1) I mis-remembered the polarity of the programming pulses for the 2716 series. They are active high not active low as with the 2732. So the GQ-4X does the right thing. The pulse length can go outside of specification, but only for bad EPROMs which do not respond to shorter programming pulses.
2) The VPP was loaded to hard by the set of AMD AM2716 EPROMs I got. The EPROMs were simply faulty (or fake chinese dummies). With known good EPROMs the VPP is stable.
Forum Admin: It may be best to delete this thread to not confuse others.
I have now tried with M2716F1 EPROMs made by ST and they work perfectly every time. They require a 21V VPP.
As to the two problems I described above:
1) I mis-remembered the polarity of the programming pulses for the 2716 series. They are active high not active low as with the 2732. So the GQ-4X does the right thing. The pulse length can go outside of specification, but only for bad EPROMs which do not respond to shorter programming pulses.
2) The VPP was loaded to hard by the set of AMD AM2716 EPROMs I got. The EPROMs were simply faulty (or fake chinese dummies). With known good EPROMs the VPP is stable.
Forum Admin: It may be best to delete this thread to not confuse others.
Thanks Tom Hunter
This thread may also help others understand troubles introduced by user measurement error and bad or fake chips.
GQ-4X does not support 2716 EPROMs
Posted - 03/10/2018 : 06:53:27
