HT85F2270 datasheet(141/226 Pages) HOLTEK

141 / 226 page

Rev. 1.00

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

Timer 2

Timer 2 is a 16-bit wide count-up counter which is driven by a user selectable internal or external

clock source. The counter is composed of two registers, TL2 and TH2, to implement the Timer,

event counter and gated timer functions. The clock source is decided by the bits T2I1 and T2I0 in

the T2CON register.

Timer function

To select this function, bits T2I1 and T2I0 in the T2CON register, should be set to “01” respectively.

The value in the Timer 2 registers, TL2 and TH2, increases by one each time an internal clock

pulse is received. The count rate is derived from the “fSYS”. The prescaler can be managed by

the T2PRE1 and T2PRE0 bits in the TMPRE register. When the timer counter is overflowed, an

interrupt will take place and the interrupt request flag, TF2, will be set to high.

Event Counter function

To select this function, bits T2I1 and T2I0 in the T2CON register, should be set to “10” respectively.

The value in the Timer 2 registers, TL2 and TH2, increases by one each time a falling edge occurs

on the external timer pin, T2. When the timer counter is overflowed, an interrupt will take place

and the interrupt request flag, TF2, will be set to high. The maximum count rate is 1/4 of the

system clock frequency.

Gated Timer function

To select this function, bits T2I1 and T2I0 in the T2CON register, should be set to “11” respectively.

The value in the Timer 2 registers, TL2 and TH2, increases by one each time an internal clock

pulse is received. The count rate is derived from the “fSYS” and the prescaler can be managed by

the T2PRE1 and T2PRE0 bits in the TMPRE register. The external timer pin, T2, can be a gate to

the Timer 2 input. When the T2 pin is set high, the Timer 2 keeps counting and when the Timer 2

is cleared to low, the Timer 2 will be stopped. The T2 input signal will be sampled once by every

internal system clock. When the timer counter is overflowed, an interrupt will take place and the

interrupt request flag, TF2, will be set to high.

HT85F2270 Datasheet(PDF) 141 Page - Holtek Semiconductor Inc