TMR0 will always use the divide by 4 for it's clock. Therefore a 4Mhz crystal will increment the TMR0 every 1uS ( 1Mhz) if the pre scaler is set to 1:1. This will always be the case regardless of the crystal frequency. Thanks Ray Doerr -----Original Message----- From: Steven Kosmerchock To: PICLIST@MITVMA.MIT.EDU Date: Thursday, January 07, 1999 10:46 AM Subject: Timer/Counter Clock Question. Friends, I was reading about the TMRO on the PIC and I was wondering about the clock it uses to divide using the prescaler. If I select the internal clock, does it use the input frequency (4MHz OSC) or the 1MHz clock that the PIC instructions run at? Also, if I select an external clock of say 32KHz, will it use that frequency inputed into the prescaler or is their a divide by 4 their as well? Thanks in advance ........................ ! Best regards, Steven ****************************************************************** Steven Kosmerchock CELWAVE Phoenix Arizona USA Email: steve.kosmerchock@celwave.com www.geocities.com/researchtriangle/lab/6584 ******************************************************************