We are seeing an odd problem with the TL16C752B Dual UART chips where our controller is unable to clear an interrupt.
We have been using these chips in our system for 6years now and on several occasions we have seen this problem.
When the chip is in this 'stuck interrupt' mode we are seeing the following values in its registers: RHR: 0x30 IER: 0x0f IIR: 0xc6 LCR: 0x03 MCR: 0x08 LSR: 0xe0 MSR: 0x00 SPR: 0xaa None of these values change when RHR is read repeatedly. What seems odd, and what is causing our system to lock up is that IIR[5-1] is indicating a Line Status interrupt. LSR[8] indicates that there is an error somewhere in the fifo yet the LSR[0] bit is indicating that the Rx fifo is empty. This appears to be contradictory.
Our controller attempts to read RHR until IIR[0] is asserted, however this is not occurring, this remains to be true even with all input Rx signals disconnected. We are supplying this UART with a 3V3 supply and driving it with a 7.3728MHz crystal.
Any insight into this problem would be appreciated.
Thanks.
Dan
