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8XC251SA, SB, SP, SQ USER'S MANUAL
TMOD
Timer/Counter Mode Control Register. Contains mode select, run control select, and counter/timer
select bits for controlling timer 0 and timer 1.
7
GATE1
C/T1#
Bit
Bit
Number
Mnemonic
7
GATE1
6
C/T1#
5, 4
M11, M01
3
GATE0
2
C/T0#
1, 0
M10, M00
C-30
M11
M01
Timer 1 Gate:
When GATE1 = 0, run control bit TR1 gates the input signal to the timer
register. When GATE1 = 1 and TR1 = 1, external signal INT1 gates the
timer input.
Timer 1 Counter/Timer Select:
C/T1# = 0 selects timer operation: timer 1 counts the divided-down
system clock. C/T1# = 1 selects counter operation: timer 1 counts
negative transitions on external pin T1.
Timer 1 Mode Select:
M11 M01
0
0
Mode 0: 8-bit timer/counter (TH1) with 5-bit prescalar (TL1)
0
1
Mode 1: 16-bit timer/counter
1
0
Mode 2: 8-bit auto-reload timer/counter (TL1). Reloaded
from TH1 at overflow.
1
1
Mode 3: Timer 1 halted. Retains count.
Timer 0 Gate:
When GATE0 = 0, run control bit TR0 gates the input signal to the timer
register. When GATE0 = 1 and TR0 = 1, external signal INT0 gates the
timer input.
Timer 0 Counter/Timer Select:
C/T0# = 0 selects timer operation: timer 0 counts the divided-down
system clock. C/T0# = 1 selects counter operation: timer 0 counts
negative transitions on external pin T0.
Timer 0 Mode Select:
M10 M00
0
0
Mode 0: 8-bit timer/counter (T0) with 5-bit prescaler (TL0)
0
1
Mode 1: 16-bit timer/counter
1
0
Mode 2: 8-bit auto-reload timer/counter (TL0). Reloaded
from TH0 at overflow.
1
1
Mode 3: TL0 is an 8-bit timer/counter. TH0 is an 8-bit timer
using timer 1's TR1 and TF1 bits.
Address:
Reset State:
GATE0
C/T0#
Function
S:89H
0000 0000B
0
M10
M00
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