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We are using the 16450 with a 68HC11F1, but in interrupt mode. The interrupt of the UART is connected to the INT line of the 68HC11 thru an open collector gate. The interrupt line is also connected to a portso that the interrupt routine can determine who is calling (this is only necessary if you've got more than one interrupt chip). Our main program store and retrieve information from a RAM buffer, which is used by the interrupt routine to send and receive data. I must admit we haven't tested at speed of 38kbps and above because our present application does not require it...but the interrupt driven software will be faster than the polling driven one. One thing you must take into account is the baudrate versus the 68HC11 working frequency. At 38kbps you got about 26us bit which makes roughly 250us for a byte to be sent by the UART. A cycle of 250us correspond to 4kHz, so the 68HC11 should have a much bigger working frequency... Using the interrupt driven UART is similar to the internal SCI where the maximum baudrate is : (Fosc / 4) / 16. To get at and above 38kbps, the 68HC11 main ocsillator must be much above : 38000 * 16 * 4 = 2.432 MHz if you want to have some time slack to do something else than sending data to the UART. Hope this help. Jean-Luc Lehmann "Peter Mackel" <peter_mackel@thermo To: <> max.co.uk> cc: Subject: RE: [m68HC11] PC16550D UART with HC11E1 26.07.02 10:20 Please respond to m68HC11 Hi Has anyone tried connecting a PC16550D UART to a 68HC11E1? I finding it difficult to fully utilise the higher baud rates that it offers. I can transmit at 38K, but my time between bytes (where I have to poll the UART to ensure the previous byte has been sent) practically halves my baud rate. I've connected the interrupt line from the UART to the HC11's PortA, and I use a falling edge on PORT A to trigger my interrupt rountines. Just interested if anyone else has used it and if they experienced any funnies. Regards Pete Yahoo! Groups Sponsor ADVERTISEMENT (Embedded image moved to file: pic05816.gif) To unsubscribe from this group, send an email to: Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. [Non-text portions of this message have been removed]

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