32
Data Sheet
FlashFlex51 MCU
SST89E52RD2/RD / SST89E54RD2/RD / SST89E58RD2/RD
SST89V52RD2/RD / SST89V54RD2/RD / SST89V58RD2/RD
©2006 Silicon Storage Technology, Inc. S71255-05-000 5/06
Symbol Function
TF2 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.
EXF2 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).
RCLK 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.
TCLK 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 overflow to be used for
the transmit clock.
EXEN2 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.
TR2 Start/stop control for Timer 2. A logic 1 starts the timer.
C/T2# Timer or counter select (Timer 2)
0: Internal timer (OSC/6 in 6 clock mode, OSC/12 in 12 clock mode)
1: External event counter (falling edge triggered)
CP/RL2# 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.
Symbol Function
X Don’t Care
- Not implemented, reserved for future use.
Note: User should not write ‘1’s to reserved bits. The value read from a reserved bit is indeterminate.
T2OE Timer 2 Output Enable bit.
DCEN Down Count Enable bit. When set, this allows Timer 2 to be configured as an up/down
counter.
Timer/Counter 2 Control Register (T2CON)
Location76543210Reset Value
C8H TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2# CP/RL2# 00H
Timer/Counter 2 Mode Control (T2MOD)
Location76543210Reset Value
C9HX-----T2OEDCENxxxxxx00b
