SM59R16A5/SM59R09A5/SM59R05A5
8-Bit Micro-controller
64KB/36KB/20KB with ISP Flash
& 2KB RAM embedded
7. Timer 0 and Timer 1
The SM59R16A5 has three 16-bit timer/counter registers: Timer 0, Timer 1 and Timer 2. All can be configured for counter
or timer operations.
In timer mode, the Timer 0 register or Timer 1 register is incremented every 12 machine cycles, which means that it
counts up after every 12 periods of the clk signal.
In counter mode, the register is incremented when the falling edge is observed at the corresponding input pin T0or T1.
Since it takes 2 machine cycles to recognize a 1-to-0 event, the maximum input count rate is 1/2 of the oscillator
frequency. There are no restrictions on the duty cycle, however to ensure proper recognition of 0 or 1 state, an input
should be stable for at least 1 machine cycle.
Four operating modes can be selected for Timer 0 and Timer 1. Two Special Function registers (TMOD and TCON) are
used to select the appropriate mode.
Mnemonic
TL0
TH0
TL1
TH1
TMOD
TCON
7.1.
Description
Timer 0 , low byte
Timer 0 , high
byte
Timer 1 , low byte
Timer 1 , high
byte
Timer Mode
Control
Timer/Counter
Control
Direct
8Ah
8Ch
8Bh
8Dh
89h
88h
GATE
TF1
C/T
TR1
M1
TF0
Bit 7
Bit 6
Bit 5
Timer 0 and 1
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
RESET
00h
00h
00h
00h
C/T
IT1
M1
IE0
M0
IT0
00h
00h
TL0[7:0]
TH0[7:0]
TL1[7:0]
TH1[7:0]
M0
TR0
GATE
IE1
Timer/counter mode control register (TMOD)
Mnemonic: TMOD
7
6
5
GATE
C/T
M1
Timer 1
4
M0
3
GATE
2
1
C/T
M1
Timer 0
Address: 89h
0
Reset
M0
00h
GATE: If set, enables external gate control (pin INT0 or INT1 for Counter 0 or 1, respectively).
When INT0 or INT1 is high, and TRx bit is set (see TCON register), a counter is
incremented every falling edge on T0 or T1 input pin
C/T: Selects Timer or Counter operation. When set to 1, a counter operation is performed,
when cleared to 0, the corresponding register will function as a timer.
M[1:0]: Selects mode for Timer/Counter 0 or Timer/Counter 1.
M1
M0
Mode
Function
0
0
Mode0
13-bit counter/timer, with 5 lower bits in TL0 or TL1
register and 8 bits in TH0 or TH1 register (for Timer 0
and Timer 1, respectively). The 3 high order bits of TL0
and TL1 are hold at zero.
0
1
Mode1
16-bit counter/timer.
1
0
Mode2
8 -bit auto-reload counter/timer. The reload value is
kept in TH0 or TH1, while TL0 or TL1 is incremented
every machine cycle. When TLx overflows, a value
from THx is copied to TLx.
1
1
Mode3
If Timer 1 M1 and M0 bits are set to 1, Timer 1 stops. If
Timer 0 M1 and M0 bits are set to 1, Timer 0 acts as
two independent 8 bit timers / counters.
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M047
35
Ver.G SM59R16A5 01/2014
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
