Cant read D2716 EEPROM.. any ideas?

By: mbates14 - 2008-01-07 19:39:26

I have a sivava PCB4.5 programmer with PCB45 and PCB3 jumper settings and stuff on it. lost the papers to it long ago, but anyway...

I cant seem to get a read from any of my 2716 chips. they all read the same thing with the chip in, or out, dont matter. just a bunch of 00s and 04s toggling back and forth. I h ave all the switches set right.

any ideas?

Re: Cant read D2716 EEPROM.. any ideas?

By: DL - 2008-01-07 20:26:27

Hi,

What program version are you using and how do you have the PCB45/PCB3 headers set?

The program will tell you how to set the headers next to the ZIF socket and the DIP switch.   But you're likely to have a voltage drop problem that needs to be fixed so you can program NMOS EPROMs reliably.

2716 should program at VCC=5V (50mS programming pulse which isn't the default) and VPP=25V.   Your programmer will probably have a VCC voltage drop and difficulty generating and maintaining VPP=25V.

To measure the VCC voltage drop problem, set your programmer for 2716, enter the Test H/W tab, and with a 2716 in the socket, enable VCC and measure the voltage at pin 28, 30, or 32 on the ZIF socket.   This should draw the max current for read (might be higher when programming).   If the voltage drops below 4.75V, you can't program 2716 reliably.   If it drops below 4.5V, you can't read reliably.   My preferred fix to this problem is to add a relay in parallel with the transistor used to switch VCC.   There'll still be a small voltage drop, but it will be linear and insignificant.   Other options are to increase the base drive of the switch or to use a low saturation device.   Neither is as robust as the relay.   The "correct" solution is to have the switch/power circuit compensate for the voltage drop in the switch.   But that change is more extensive.

Problems with VPP can sometimes be fixed by using a better inductor, but I prefer to replace the step-up regulator with a more reliable linear regulator (LM317).   This requires you to use a different power supply, but makes VPP more reliable.

Whenever you have a device in the programming sockets, you must always enable VCC before VPP and disable VPP before VCC.  Failure to sequence the supplies in this order can damage the device.

HTH,
Dennis

Re: Cant read D2716 EEPROM.. any ideas?

By: mbates14 - 2008-01-07 20:42:42

no, im not trying to program the chip.

im trying to READ the chip, i cant even get a read from the chip.


i got both jumpers on PCB3, program version 0.98D5

Re: Cant read D2716 EEPROM.. any ideas?

By: mbates14 - 2008-01-07 20:58:03

ok update.. its a 24 pin chip, VCC being at 24.

well i did what you said, enabled VCC, i have 4.9v at pin 32 of the ZIF, but the chip doesnt come up this far, smaller chip. but nothing at pin24. somethign isnt right here.

Re: Cant read D2716 EEPROM.. any ideas?

By: DL - 2008-01-07 21:00:31

Hi,

Set your programmer to PCB45 if you want to use 0.98D5.  That program uses a different method for generating address and reading data.  The PCB3 option requires 0.97ja or 0.97g.

You could still have voltage drop problems that could prevent a good read.  Do the test I mentioned before to see how much VCC drops.

HTH,
Dennis

Re: Cant read D2716 EEPROM.. any ideas?

By: DL - 2008-01-07 21:03:13

Hi,
Quote:
well i did what you said, enabled VCC, i have 4.9v at pin 32 of the ZIF, but the chip doesnt come up this far, smaller chip. but nothing at pin24. somethign isnt right here.
Sounds like you don't have the jumpers next to the ZIF socket set correctly.  The program shows you how to set them.  For DIP24 devices, VCC will be at pins 28, 30, and 32 on the socket.  The programmer is hardwired for VCC to be at pin32.  One of the DIP switches routes VCC to pin30 and one of the headers next to the ZIF routes it from 30 to 28 -- or pin24 on the device.

HTH,
Dennis

Re: Cant read D2716 EEPROM.. any ideas?

By: mbates14 - 2008-01-07 21:06:34

i have the blue switch box set exactly as per the software shows.

the rest of the jumpers, i lost the paper so i dont know what none of the others are.

Re: Cant read D2716 EEPROM.. any ideas?

By: DL - 2008-01-08 02:25:03

Hi,

You need to set the jumpers next to the ZIF socket appropriately.  You don't need any documents; the program shows the setting.

HTH,
Dennis

Re: Cant read D2716 EEPROM.. any ideas?

By: mbates14 - 2008-01-08 02:59:51

my board isnt like that in the picture. its way different. thats the whole delimma.

anyway, i was able to use a regular wire between 24 and 32 or w/e pins it was, and get good reads.

thanks to being able to read the chips, i discovered the source of my issues. the chips are bad. (the chips are ROMs from an arcade machine that dont work properly).

Re: Cant read D2716 EEPROM.. any ideas?

By: DL - 2008-01-08 04:32:27

Hi,

There's not really much of a dilemma.  Sivava's programmers are still based on the PCB3 design.  All PCB3 variants I've seen have those headers.  On your programmer, they just happen to be on the other side of the PLCC32 sockets that have been added.

It would be unwise for anyone designing a PCB3 variant to change the configuration of those headers.

Before dismissing the devices as bad, you need to do the test for VCC voltage drop.  You need to check the voltage tolerance of your EPROM and make sure VCC is staying within that range.  If it drops below that, an EPROM programmed with marginal erase margin could read incorrectly.

Are you reading ROMs or EPROMs?  They don't necessarily have the same pinouts.

HTH,
Dennis

Re: Cant read D2716 EEPROM.. any ideas?

By: mbates14 - 2008-01-08 05:30:54

im reading the D2716 EPROM

the first 6 on the arcade prom board read fine. the rest read as 00s. maybe one or two show up as some data. but all chips are reading all 00s. the first 6 read just fine.

that would explain why the game crashes on bootup with scrambled video and repeating sounds.

the EPROMs on the sound board read fine. but the main ROM board only 6 read fine. rest are all 00s.