ICPROG JDM mode error when reading 16F877

ICPROG read error

Hai
I have connected a ICSP hardware to ICPROG JDM mode.( ver 1.05D)
It correctly programmes 16F877 but cant read back.
Any similer experience or fault with my hardware?
Hardware check gives ok. Logic levels are correct
it only reads first one or two locations (wrongly) all other locations are read as blank1
please give some hints. using 74HCT125E buffer arrangement for serial port interface.
Is there any chance that my PC serial port fails to sense a +5 volt as a valid input logic state.
All other functions are correct.I have confirmed the correctness of programming of this circuit with another programmer.
Please
Picstudent

Re: ICPROG read error

Hai
I have little more narrowed down my problem.

When A chip is programmed (in case of 877 programming correct but not verify)

But if we fill programe memmory with values like

0x3333, 0x7777 ,0x5555 ,0x9999 0x 1111

0x 3951 or any combinations of 1,3,5,7,9 hex numbers in programe memmorry it will programe and verify corectly

The programming voltage I am applying is 12.6 volts
Please help.I am in a deadlock for days!!
Picstudent

Re: ICPROG read error

It is quite possible that the PC will not correctly read signals from 74HC125 as it is only 0-5V. Can you try proper RS-232 driver (max202, 232, .. or similar)?

Re: ICPROG read error

hai
Thanks for the response.
But to confuse things up I have noticed another issue.
The above mentioned symptom is when programming 16F877.
I tried 16F73. In this case it cannot even programe correctly. that means data outside of pc is also found corrupted.

But for both chips the above values I mentioned are programmed and verified correctly.
Any chance that the problem with programming voltage .I have another programmer .they are using some 13.8 volts as Vpp.is it required?

Different pic,different symptoms.In one case data in currupt,in another both are corrupt.Will it points that problem is elsewhere. Vpp? or VPP rise time or anything like that? No capacitors on lines .Just 0.001 on VPP.Tried by removing also.
Give possibilities you feel .Please. For max 232, I will try as a last resort
Picstudent

Re: ICPROG read error

Data sheets for both PIC have 14V (max) for 877 and 13.5V (max) for 73, so I would assume that 12.5 and higher should be enough.
I still think you have a problem with RS-232. How do you controll 74125, or do you have the control pins connected directly to 0V?

Re: ICPROG read error

If you are using any Windows NT based OP (win2k sau xp) use in Hardware Settings Windows API and close any other applicattions.

Re: ICPROG read error

hai
thanks for the suggessions.

I am using win98 and the same driver in JDM mode drives another semi -commercial programmer and is working ok. But in that hardware the data- in pin swings from -.65V to 5V of serial port. But my hardware swings from 0 to 5 only.

74HCT125E enable pins are shorted and connected to GND through a jumper. No pull ups on any pins of 74HC125E. But when that pin is not shorted to gnd and left floating ,the buffer doesnt seems to be isolated-something is passing between .Will that or any other pin requires pull up for 74HCT125E? Datasheet seems to be silent about that aspect!
When we use ICD it pulls down the MCLR pin to GND. but this ICSP ckt cant do that. Any issue there?
Thanks for all the sugessions.
Please
Picstudent

Re: ICPROG read error

Problem with 125 as RS-232 driver is that it doesn't reverse the phase: you need to negate both signals (Rx and Tx).
Attached is a circuit that "steels" negative power from DB9 and negates both signals.
Try it..

Re: ICPROG read error

Hai
Thanks IanP for the ckt and hint.your solution solved the issue. Now it is working. With your 'stealing ' technique.It is working now.

To my annoyence sometimes still the programer fails to programe ,reads alright. But think some programmer voltage or wiring error.Feels it can be located. but any clue will be helpful. (only fails to programe,read ok)

When the programmer is working alright ,if just switch the power supply to the programmer off and again switched on , it wont work. any area of possible trouble ?
Again thanks ,the dead lock is over.

Picstudent

Re: ICPROG read error

Hi,
You can use Propic2 hardware on ICPROG.Also use CD4050B instead of TTL ICs.
I am using it for more than 2 years with no problems.
Regards
Aji

Re: ICPROG read error

Hai

Will Propic2 support ICSP ?
I have previously built propic2 and is working, but without ICSP.

Thanks

Picstudent

Re: ICPROG read error

This can be a COM port issue as for "steeling" option you need at least one of the control (RTS-CTS, ...)/Tx lines to be "low".
You can always try a terminal software to set/reset the control lines which will give you some extra power to supply this ciruit ..