Question

14.5. Give the name of the bit, the name of the register that it is in, the register's address, which bit, and the default or reset state of the bit for each of the following:

a-What bit indicates that the timer has overflowed?

b-What bit enables the timer overflow interrupts?

c-What bits are used to prescale the timer clock?

Answer 1

IN 8051 microcontroller, There are 3 Timers out of which 2 are internal timers, let it be T0 and T1

these are 16 bit timer and can be used as counters as well, the overflow of timers is indicated in Timer Control Register(TCON).

TCON is a 8-bit register,upper bits are responsible for timers or counters and lower bits are responsible for interrupts.

the TCON register contents are TF1 | TR1 | TF0 | IE1 | IT1 | IE0 | IT0

TF1 and TF0 represents timer overflow flags for T1 and T0 respectively,

when the timer (Tx) changes from all 1's to 0, TFx will be set to 1

Prescaling of timer clock will be done by Prescaler. Prescaler is a electronic device used to reduce high frequency signal to low frequency signal using division(with integers), it helps user to have a specific frequency as desired.