Figure 21) – Rainbow Electronics T89C51CC01 User Manual
Page 58
58
T89C51CC01
Rev. D – 17-Dec-01
Table 21. TMOD Register
TMOD (S:89h)
Timer/Counter Mode Control
Register.
Reset Value= 0000 0000b
7
6
5
4
3
2
1
0
GATE1
C/T1#
M11
M01
GATE0
C/T0#
M10
M00
Bit
Number
Bit
Mnemonic
Description
7
GATE1
Timer 1 Gating Control Bit
Clear to enable Timer 1 whenever TR1 bit is set.
Set to enable Timer 1 only while INT1# pin is high and TR1 bit is set.
6
C/T1#
Timer 1 Counter/Timer Select Bit
Clear for Timer operation: Timer 1 counts the divided-down system clock.
Set for Counter operation: Timer 1 counts negative transitions on external pin T1.
5
M11
Timer 1 Mode Select Bits
M11 M01 Operating mode
0
0
Mode 0: 8-bit Timer/Counter (TH1) with 5-bit prescaler (TL1).
0
1
Mode 1: 16-bit Timer/Counter.
1
0
Mode 2: 8-bit auto-reload Timer/Counter (TL1).
(a)
1
1
Mode 3: Timer 1 halted. Retains count
4
M01
3
GATE0
Timer 0 Gating Control Bit
Clear to enable Timer 0 whenever TR0 bit is set.
Set to enable Timer/Counter 0 only while INT0# pin is high and TR0 bit is set.
2
C/T0#
Timer 0 Counter/Timer Select Bit
Clear for Timer operation: Timer 0 counts the divided-down system clock.
Set for Counter operation: Timer 0 counts negative transitions on external pin T0.
1
M10
Timer 0 Mode Select Bit
M10 M00 Operating mode
0
0
Mode 0: 8-bit Timer/Counter (TH0) with 5-bit prescaler (TL0).
0
1
Mode 1: 16-bit Timer/Counter.
1
0
Mode 2: 8-bit auto-reload Timer/Counter (TL0).
(b)
1
1
Mode 3: TL0 is an 8-bit Timer/Counter
TH0 is an 8-bit Timer using Timer 1’s TR0 and TF0 bits.
0
M00
a.
Reloaded from TH1 at overflow.
b.
Reloaded from TH0 at overflow.