Information

PIC16C63A

1999 Microchip Technology Inc. DS80015B-page 3
3. Module: TMR1
When operating in external clock mode (TMR1CS is
set), reading either of the timer 1 registers (TMR1H
or TMR1L) may cause the timer not to increment as
expected. This occurs for both synchronous and
asynchronous inputs.
The scenarios which display this are:
• When a read operation of the TMR1H register
occurs, the TMR1L register may not increment.
• When a read operation of the TMR1L register
occurs, the TMR1H register may not increment.
This improper operation is only an issue when
the TMR1L register increments from FFh to 00h
(FFh → 00H) during the read of the TMR1L reg-
ister.
Work Around
Do not read either the TMR1H or the TMR1L regis-
ters when operating in external clock mode
(TMR1CS is set). If the application needs to read the
16-bit counter, evaluate if this function can be moved
to the TMR0 or one of the other timer resources on
the device.