Rainbow Electronics T89C51RD2 - Manual (Page 20)

20 Rev. F - 15 February, 2001
T89C51RD2
Table 5. T2CON Register
T2CON - Timer 2 Control Register (C8h)
Reset Value = 0000 0000b
Bit addressable
7 6 5 4 3 2 1 0
TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2# CP/RL2#
Bit
Number
Bit
Mnemonic
Description
7 TF2
Timer 2 overflow Flag
Must be cleared by software.
Set by hardware on timer 2 overflow, if RCLK = 0 and TCLK = 0.
6 EXF2
Timer 2 External Flag
Set when a capture or a reload is caused by a negative transition on T2EX pin if EXEN2=1.
When set, causes the CPU to vector to timer 2 interrupt routine when timer 2 interrupt is enabled.
Must be cleared by software. EXF2 doesn’t cause an interrupt in Up/down counter mode (DCEN = 1)
5 RCLK
Receive Clock bit
Clear to use timer 1 overflow as receive clock for serial port in mode 1 or 3.
Set to use timer 2 overflow as receive clock for serial port in mode 1 or 3.
4 TCLK
Transmit Clock bit
Clear to use timer 1 overflow as transmit clock for serial port in mode 1 or 3.
Set to use timer 2 overflow as transmit clock for serial port in mode 1 or 3.
3 EXEN2
Timer 2 External Enable bit
Clear to ignore events on T2EX pin for timer 2 operation.
Set to cause a capture or reload when a negative transition on T2EX pin is detected, if timer 2 is not used to
clock the serial port.
2 TR2
Timer 2 Run control bit
Clear to turn off timer 2.
Set to turn on timer 2.
1 C/T2#
Timer/Counter 2 select bit
Clear for timer operation (input from internal clock system: F
OSC
).
Set for counter operation (input from T2 input pin, falling edge trigger). Must be 0 for clock out mode.
0 CP/RL2#
Timer 2 Capture/Reload bit
If RCLK=1 or TCLK=1, CP/RL2# is ignored and timer is forced to auto-reload on timer 2 overflow.
Clear to auto-reload on timer 2 overflows or negative transitions on T2EX pin if EXEN2=1.
Set to capture on negative transitions on T2EX pin if EXEN2=1.