at89c55-12qi ATMEL Corporation, at89c55-12qi Datasheet - Page 6

• Manufacturer Part Number: at89c55-12qi
• Description: 8-bit Microcontroller With Bytes Flash
• Manufacturer: ATMEL Corporation

Table 2. T2CON—Timer/Counter 2 Control Register
6
Symbol
TF2
EXF2
RCLK
TCLK
EXEN2
TR2
C/T2
CP/RL2
T2CON Address = 0C8H
Bit Addressable
Bit
TF2
Function
Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2 will not be set
when either RCLK = 1 or TCLK = 1.
Timer 2 external flag set when either a capture or reload is caused by a negative transition on T2EX
and EXEN2 = 1. When Timer 2 interrupt is enabled, EXF2 = 1 will cause the CPU to vector to the
Timer 2 interrupt routine. EXF2 must be cleared by software. EXF2 does not cause an interrupt in
up/down counter mode (DCEN = 1).
Receive clock enable. When set, causes the serial port to use Timer 2 overflow pulses for its receive
clock in serial port Modes 1 and 3. RCLK = 0 causes Timer 1 overflow to be used for the receive
clock.
Transmit clock enable. When set, causes the serial port to use Timer 2 overflow pulses for its
transmit clock in serial port Modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the
transmit clock.
Timer 2 external enable. When set, allows a capture or reload to occur as a result of a negative
transition on T2EX if Timer 2 is not being used to clock the serial port. EXEN2 = 0 causes Timer 2 to
ignore events at T2EX.
Start/Stop control for Timer 2. TR2 = 1 starts the timer.
Timer or counter select for Timer 2. C/T2 = 0 for timer function. C/T2 = 1 for external event counter
(falling edge triggered).
Capture/Reload select. CP/RL2 = 1 causes captures to occur on negative transitions at T2EX if
EXEN2 = 1. CP/RL2 = 0 causes automatic reloads to occur when Timer 2 overflows or negative
transitions occur at T2EX when EXEN2 = 1. When either RCLK or TCLK = 1, this bit is ignored and
the timer is forced to auto-reload on Timer 2 overflow.
7
AT89C55
EXF2
6
RCLK
5
TCLK
4
EXEN2
3
TR2
2
Reset Value = 0000 0000B
C/T2
1
CP/RL2
0