Hi, I'm using an 89C51RD2 chip and an Texas Instruments TL16C754B Quad UART chip for serial communication. At power-on, a random character gets transmitted on all 4 channels of the UART. Can someone please tell me why this may be happening and how to prevent it? Thanks and warm regards, Sundeep
aka initialization error. i guess you are either Unintentionally clocking the UART because of bad initialize. Not initializing the UART. Not holding the UART in reset as required. or pointing to "empty space" because pointer not initialized Erik
Thanks Erik. But the RST pin of the controller is connected to the RESET pin of the UART. So, the UART starts functioning only after the Controller has reset. So, I think the unintentional clocking is ruled out? -Sundeep.
But the RST pin of the controller is connected to the RESET pin of the UART. So, the UART starts functioning only after the Controller has reset. The RST pin is an input, what is driving it? Erik
But the RST pin of the controller is connected to the RESET pin of the UART. So, the UART starts functioning only after the Controller has reset.
But the RST pin of the controller is connected to the RESET pin of the UART. So, the UART starts functioning only after the Controller has reset. RST is an input, what drives it? Erik
But the RST pin of the controller is connected to the RESET pin of the UART. So, the UART starts functioning only after the Controller has reset. RST is an input, what generates it? Erik
as you see above repeats, the slovenly response of this site cabn give unexpected results. This was entered once only without timeout. Erik
An ADM709 RST circuit drives the RST pin. -Sundeep
It may be the case that you cannot easily prevent whatever receiver is connected to your transmitting UART from seeing a character on powerup. I think that the receiver may require as little as a change of state of the receive line to believe a character is incoming. Stefan
An ADM709 RST circuit drives the RST pin. This chip generates Reset LOW, the uC require reset HIGH. There must be more to it Erik
A invertor is connected between the uC and the ADM709 circuit. Therefore reset HIGH is fed to the RST pin of uC. The same line is also fed to the RESET pin of the UART. The RESET pin the UART is an active high input. -Sundeep
A invertor is connected between the uC and the ADM709 circuit. That, I believe is your problem. As the Power is ramping up a supervisor behaves in a predicatble way, an inverter behaves any which way it wants till its minimum operating voltage is reached. I have seen this design resulting in too short and/or erratic reset pulses. Get a reset high supervisor and use it. Erik
Thanks Erik. I think this is the problem too. -Sundeep