AT89C51RE2 Atmel Corporation, AT89C51RE2 Datasheet - Page 74

• Manufacturer Part Number: AT89C51RE2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RE2

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Spi: 1
• Uart: 2
• Sram (kbytes): 8.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART/OCD
• Watchdog: Yes

74
AT89C51RE2
Table 47. TMOD Register
TMOD (S:89h)
Timer/Counter Mode Control Register
Notes: 1. Reloaded from TH1 at overflow.
Reset Value = 0000 0000b
Bit Number
GATE1
7
7
6
5
4
3
2
1
0
2. Reloaded from TH0 at overflow.
Mnemonic
C/T1#
GATE1
GATE0
C/T1#
C/T0#
M11
M01
M10
M00
Bit
6
Description
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.
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.
Timer 1 Mode Select Bits
M11
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.
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.
Timer 0 Mode Select Bit
M10
TH0 is an 8-bit Timer using Timer 1’s TR0 and TF0 bits.
0
0
1
1
0
0
1
1
M11
5
M01
0
1
0
1
M00
0
1
0
1
M01
4
Mode 2: 8-bit auto-reload Timer/Counter (TL0)
Mode 3: TL0 is an 8-bit Timer/Counter
Operating mode
Mode 0: 8-bit Timer/Counter (TH0) with 5-bit prescaler (TL0).
Mode 1: 16-bit Timer/Counter.
Operating mode
Mode 0: 8-bit Timer/Counter (TH1) with 5-bit prescaler (TL1).
Mode 1: 16-bit Timer/Counter.
Mode 2: 8-bit auto-reload Timer/Counter (TL1)
Mode 3: Timer 1 halted. Retains count
GATE0
3
C/T0#
2
M10
1
(2)
7663E–8051–10/08
(1)
M00
0