
C8051T610/1/2/3/4/5/6/7
25.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures Timer 0 and Timer 1 to operate as 8-bit counter/timers with automatic reload of the start
value. TL0 holds the count and TH0 holds the reload value. When the counter in TL0 overflows from all
ones to 0x00, the timer overflow flag TF0 in the TCON register is set and the counter in TL0 is reloaded
from TH0. If Timer 0 interrupts are enabled, an interrupt will occur when the TF0 flag is set. The reload
value in TH0 is not changed. TL0 must be initialized to the desired value before enabling the timer for the
first count to be correct. When in Mode 2, Timer 1 operates identically to Timer 0.
Both counter/timers are enabled and configured in Mode 2 in the same manner as Mode 0. Setting the
TR0 bit (TCON.4) enables the timer when either GATE0 in the TMOD register is logic 0 or when the input
TMOD
IT01CF
G
A
C
/
T T
1 1
G
A
C
/
T T
0 0
I
N
I
N
I
N
I
N
I
N
I
N
I
N
I
N
T0M
T
E
T
1
M M
1 0
T
E
T
0
M M
1 0
1
P
1
S
1
S
1
S
0
P
0
S
0
S
0
S
1
0
L
L
L
L
L
L
L
L
2
1
0
2
1
0
Pre-scaled Clock
SYSCLK
0
1
0
1
T0
TF1
Crossbar
GATE0
TR0
TCLK
TL0
(8 bits)
TH0
Reload
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Interrupt
(8 bits)
INT0
IN0PL
XOR
Figure 25.2. T0 Mode 2 Block Diagram
174
Rev 1.1