I'm using a Cypress CY7C68013A on their CY3684/3674 EZ-USB Advanced Development Board. If I change the 8051's clock rate from 48MHz to either 24MHz or 12MHz the Keil debugger stops. I am trying to determine if a slower clock rate would reduce the noise on the board. The debugger is using a COM port, so my suspicion is that the COM port frequency needs to be changed if the CPU frequency is changed?
The noise issues I'm having are; One of the LEDs changes when writing to another one. Sometimes the empty flags don't go off when I send USB data. The data does get sent as after x transfers the buffering is full, though empty wasn't seen. I've set breakpoints on the test for empty, and I've tested them to set LED status. EP2FIFOFLGS and EP24FIFOFLGS never set EP2 empty flag low.
Assuming this is the issue is there a routine I can call to change the clock and the COM port output together?