Post by thread:[PIC]: 16F877 usart

Hi, I've been working with a PIC16F877 today primarily with the usart(sci) port and have come up against what appears to be a local echo within the IC. Whatever I transmit immediately appears at the rx pin ( I have even lifted the RX leg to make sure that there is not a short causing this). Is this to be expected with this device - I certainly could not see anything in the specs. Best regards, John -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> Whatever I transmit immediately appears at the rx pin John, I've had a 16F877 designed into a product for about 6 weeks now and have never seen this. Wynn Rostek -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> I've been working with a PIC16F877 today primarily with the usart(sci) port > and have come up against what appears to be a local echo within the IC. > Whatever I transmit immediately appears at the rx pin ( I have even lifted > the RX leg to make sure that there is not a short causing this). > Is this to be expected with this device - I certainly could not see anything > in the specs. The USART in normal asynchronous mode definitely does not do this. I've used it many times, and such an echo would have messed quite a few projects. However, I don't understand exactly what you mean by "usart(sci)". ***************************************************************** Olin Lathrop, embedded systems consultant in Devens Massachusetts (978) 772-3129, spam_OUTolinTakeThisOuTembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>However, I don't understand exactly what you mean by "usart(sci)". Means he graduated from Mot to Microchip. Andy -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Actually I was just reflecting what Microchip called the port in their literature but to be clear I am using said port in it's Asynchronous mode. I still have the problem and it's definitely in the chip (both of them - I have two!), but I've put in a workaround by not switching on the RX logic until I want it and when I do I clear out the FIFO (2 deep buffer) before accepting any data. I have a DIP '877 somewhere at home which I'll try also. I'm using the Hitech SCI (oops theres theat word again)code sample which works admirably for me on other devices. I've checked this and it all appears ok. If I figure out the cause I'll let you know John -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics