P87C52 PHILIPS [NXP Semiconductors], P87C52 Datasheet - Page 11

• Manufacturer Part Number: P87C52
• Description: 80C51 8-bit microcontrollers 16K/32K, 512 OTP, I2C, watchdog timer
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
2000 Aug 07
80C51 8-bit microcontroller family
4 K/8 K OTP/ROM low voltage (2.7 V–5.5 V),
low power, high speed (33 MHz), 128/256 B RAM
T2EX Pin
Symbol
TF2
EXF2
RCLK
TCLK
EXEN2
TR2
C/T2
CP/RL2
T2 Pin
OSC
Position
T2CON.7
T2CON.6
T2CON.5
T2CON.4
T2CON.3
T2CON.2
T2CON.1
T2CON.0
12
Transition
Detector
(MSB)
TF2
C/T2 = 0
C/T2 = 1
Name and Significance
Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2 will not be set
when either RCLK 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 flag. When set, causes the serial port to use Timer 2 overflow pulses for its receive clock
in modes 1 and 3. RCLK = 0 causes Timer 1 overflow to be used for the receive clock.
Transmit clock flag. When set, causes the serial port to use Timer 2 overflow pulses for its transmit clock
in modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the transmit clock.
Timer 2 external enable flag. 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. A logic 1 starts the timer.
Timer or counter select. (Timer 2)
Capture/Reload flag. When set, captures will occur on negative transitions at T2EX if EXEN2 = 1. When
cleared, auto-reloads will occur either with Timer 2 overflows or negative transitions at T2EX when
EXEN2 = 1. When either RCLK = 1 or TCLK = 1, this bit is ignored and the timer is forced to auto-reload
on Timer 2 overflow.
EXF2
EXEN2
0 = Internal timer (OSC/12)
1 = External event counter (falling edge triggered).
Figure 1. Timer/Counter 2 (T2CON) Control Register
Control
RCLK
Figure 2. Timer 2 in Capture Mode
TR2
Control
Capture
TCLK
11
RCAP2L
(8-bits)
EXEN2
TL2
(8-bits)
RCAP2H
TR2
TH2
80C51/87C51/80C52/87C52
C/T2
EXF2
TF2
CP/RL2
(LSB)
Product specification
SU00728
SU00066
Interrupt
Timer 2