HT85F2270 datasheet(138/226 Pages) HOLTEK

138 / 226 page

Rev. 1.00

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

Mode 3 – Two 8-Bit Timers/Counters Mode Operation – Timer 0 Only

To select this mode, bits T0M1 and T0M0, should be set to “11” respectively. This mode is only

available for Timer 0. For Timer 1 and Timer 3, this mode is not available and if selected will stop

the timer function. The two 8-bit Timer/Counter function is implemented by the two individual 8-bit

TL0 and TH0 registers. TL0 can have both Timer and Counter functions while TH0 can only have

a Timer function. The C/T0 bit is used to select the timer or counter function for TL0. The TL0

Run or Stop is controlled by the TR0 bit. If the Counter function is selected, the TR0 and GATE0

bits can be used to manage the external INT0 input to count external edge transitions or to measure

input pulse widths. If the TL0 counter overflows, an interrupt will be generated and the interrupt

request flag, TF0, will be set high. The timer/counter clock source is decided by the T0PRE0 and

T0PRE1 bits in the TMPRE register.

In addition to TL0, the other 8-bit timer, TH0, can use the TR1 bit to enable the Timer. If the TH0

counter overflows, an interrupt will be generated and the interrupt request flag, TF1, will be set

high. The timer clock source is decided by the T0PRE0 and T0PRE1 bits in the TMPRE register.

The following block illustrates the two 8-bit Timer/Counters basic operational blocks.

fSYS

TR0

GATE0

INT0

TL0

TH0

TR1

fSYS/4

fSYS

fSYS/6

fSYS/1�

T0PRE[1:0]

C/T0=0

C/T0=1

�UX

Interrupt TF1 flag

Interrupt TF0 flag

Mode 3 Block Diagram – Timer 0

HT85F2270 Datasheet(PDF) 138 Page - Holtek Semiconductor Inc