SN8P2740 Series
ADC, OP-amp, Comparator 8-Bit Micro-Controller
8.2 T0 8-BIT BASIC TIMER
8.2.1 OVERVIEW
The T0 timer is an 8-bit binary up timer with basic timer function. The basic timer function supports flag indicator
(T0IRQ bit) and interrupt operation (interrupt vector). The interval time is programmable through T0M, T0C registers.
The T0 builds in green mode wake-up function. When T0 timer overflow occurs under green mode, the system will be
waked-up to last operating mode.
8-bit programmable up counting timer: Generate time-out at specific time intervals based on the selected clock
frequency.
Interrupt function: T0 timer function supports interrupt function. When T0 timer occurs overflow, the T0IRQ
actives and the system points program counter to interrupt vector to do interrupt sequence.
Green mode function: T0 timer keeps running in green mode and wakes up system when T0 timer overflows.
T0 Rate
(Fcpu/2~Fcpu/256)
Load T0C Value by Program.
T0ENB
Fcpu
T0IRQ Interrupt Flag
(T0 timer overflow.)
T0C 8-Bit Binary Up Counting Counter
CPUM0,1
8.2.2 T0 TIMER OPERATION
T0 timer is controlled by T0ENB bit. When T0ENB=0, T0 timer stops. When T0ENB=1, T0 timer starts to count. T0C
increases “1” by timer clock source. When T0 overflow event occurs, T0IRQ flag is set as ”1” to indicate overflow and
cleared by program. The overflow condition is T0C count from full scale (0xFF) to zero scale (0x00). T0 doesn‟t build in
double buffer, so load T0C by program when T0 timer overflows to fix the correct interval time. If T0 timer interrupt
function is enabled (T0IEN=1), the system will execute interrupt procedure. The interrupt procedure is system program
counter points to interrupt vector (ORG 8) and executes interrupt service routine after T0 overflow occurrence. Clear
T0IRQ by program is necessary in interrupt procedure. T0 timer can works in normal mode, slow mode and green
mode. In green mode, T0 keeps counting, set T0IRQ and wakes up system when T0 timer overflows.
Clock
Source
...
...
...
...
0x00 or “n”
by program
0x01
or n+1
0x02
or n+2
0x02
or n+2
0x00 or “n”
by program
T0C
0xFE
0xFF
T0IRQ
T0 timer overflows. T0IRQ set as “1”.
Reload T0C by program.
T0IRQ is cleared by program.
SONiX TECHNOLOGY CO., LTD
Page 77
Version 2.0
SONIX [ SONIX TECHNOLOGY COMPANY ]
