P89V51RD2 - No "Reset Now " message

[micronathan]

I have been using FM for long but since yesterday I am stuck totally.

Downloaded the latest version 4.66.1635 from the net. MCU runs with 11.0952 MHz crystal is 6-clk mode.

I have a working ( earlier ) PCB with the 89V51RD2 on it. When I connect and try to read the device signature now , I can see the "Attempting to connect " message and then after the time-out, the pop up about the failure to connect, try lower baud rate etc. Normally when I want to read the Device, I used to get the "Reset Device now" pop-up. Now I don't get it - why ?

I am just using the TXD,RXD,GND pins of the COM 1 port of the PC.

1. The MAX232 is healthy.
2. The Looop Back check on the PC is fine.
3. With the PC connected to the MCU board I measure -9.1V between pin 3 and 5 of the 9-pin D Sub.

Does it mean my 89V51RD2 has its bootcode corrupted or something ?

Kindly help.

Thanks

micronathan

[Andy Ayre]

Go to Options -> Advanced Options and uncheck the "Use DTR..." setting.

Andy

[micronathan]

Hi Andy,

Thanks for the tip - I had looked into that option previously but never realized its significance. I am connecting without problems now.

While struggling earlier, I started gettin doubts on the connections to pins 2 and 3 of the RS232 connector ( 9-Pin female) and have verified that connection also now ( pin 2 -> T2OUT -> T2IN -> TxD of MCU ; Pin 3 -> R2IN -> R2OUT -> RxD of MCU ). This is the exact opposite of what has been suggested by Jon Ledbetter in his "A Simple RS232 Guide" updated 05/22/2007, but it works. Not sure how.

Actually there is a whole lot of confusion on these pins TxD and RxD ! Male , Female, 9-pin, 25-pin, DCE , DTE etc etc. The only thing I now know is that after linking the MCU to the PC, I should read around -8V on both pins 2 and 3 with respect to 5. And use a regular RS232 cable.

Regards

micronathan

[Andy Ayre]

If in doubt about connections I would suggest looking at the schematic diagrams of the Keil evaluation boards. They make the diagrams available on their website and nearly always feature an RS232 transceiver and 9-pin D-type connector. Even though the boards are for other microcontrollers, they show the UART connections which will be the same.

Andy