Flash Magic Forum

In-System Programming Support => P89C51Rx+/P89C51Rx2/P89C66x/P89C6xX2/P89V66x => Topic started by: Nikolai on January 17, 2007, 06:30:01 am

Title: 89C51RD2BN connectivity problems
Post by: Nikolai on January 17, 2007, 06:30:01 am
Im having the same old problem of "Unable to connect at specified baud rate"..

I double checked the connections. I tried communicating through the hyper terminal but "u" is also not being echoed.

any ideas as to wat could be wrong ?
Title: Re: 89C51RD2BN connectivity problems
Post by: Jan Waclawek on January 17, 2007, 09:54:03 am

What is the history of this chip? Did you already attempt to program it? Did you run it in a board with inappropriate (=RC) reset?

Jan Waclawek
Title: Re: 89C51RD2BN connectivity problems
Post by: Nikolai on January 17, 2007, 10:22:35 am
i checked the power supply...its working fine...
didnt try chucking the reset ckt...
oscillator is working fine

ISP conditions met...(PSEN pulled to GND,Vpp=5V,ALE=NC)

RS232 link is good.. i tried shorting rx n tx, n characters do echo back.

I just got a brand new IC (the second since the first failed for unknown reasons)... so lost boot vector is less probable.
Title: Re: 89C51RD2BN connectivity problems
Post by: erikm on January 18, 2007, 12:41:19 pm
do you have P2.6 and P2.7 high?

Erik
Title: Re: 89C51RD2BN connectivity problems
Post by: Nikolai on January 19, 2007, 08:26:30 am
Yes P2.6  n P2.7 is high when the circuit is powered. As a matter of fact PSEN too is high(4.93 volts) when in run mode.
Title: Re: 89C51RD2BN connectivity problems
Post by: Andy Ayre on January 24, 2007, 09:33:52 am
A brand new device should power up into ISP mode. Is that the case? If you take a new device and still cannot get the 'U' to echo back then there is something wrong with either the communication path between your PC and the device or an electrical problem.

Have you tried putting a scope on the RxD pin to see if the 'U' is getting there? If it is, put the scope on the TxD pin. Do you see the 'U'?