DS89C420-QCL Datasheet, PDF (35/139 Pages) Maxim Integrated Products – Ultra-High-Speed Flash Microcontroller User’s Guide

Ultra-High-Speed Flash
Microcontroller User’s Guide
RCLK
Bit 5
TCLK
Bit 4
EXEN2
Bit 3
TR2
Bit 2
C/T2
Bit 1
CP/RL2
Bit 0
CP/RL2 EXEN2 DCEN
RESULT
1
0
X Negative transitions on P1.1 do not affect this bit.
1
1
X Negative transitions on P1.1 set this bit.
0
0
0 Negative transitions on P1.1 do not affect this bit.
0
1
0 Negative transitions on P1.1 set this bit.
Bit toggles whenever Timer 2 underflows/overflows
0
X
1 and can be used as a 17th bit of resolution. In this
mode, EXF2 does not cause an interrupt.
Receive Clock Flag. This bit determines the serial port 0 time base when receiving data in serial
modes 1 or 3. Setting this bit forces Timer 2 into baud-rate generation mode. The timer operates
from a divide-by-2 of the external clock.
0 = Timer 1 overflow is used to determine receiver baud rate for serial port 0.
1 = Timer 2 overflow is used to determine receiver baud rate for serial port 0.
Transmit Clock Flag. This bit determines the serial port 0 time base when transmitting data in
serial modes 1 or 3. Setting this bit forces Timer 2 into baud rate generation mode. The timer operates
from a divide-by-2 of the external clock.
0 = Timer 1 overflow is used to determine transmitter baud rate for serial port 0.
1 = Timer 2 overflow is used to determine transmitter baud rate for serial port 0.
Timer 2 External Enable. This bit enables the capture/reload function on the T2EX pin if Timer 2
is not generating baud rates for the serial port.
0 = Timer 2 ignores all external events at T2EX.
1 = Timer 2 captures or reload a value if a negative transition is detected on the T2EX pin.
Timer 2 Run Control. This bit enables/disables the operation of Timer 2. Halting this timer preserves
the current count in TH2, TL2.
0 = Timer 2 is halted.
1 = Timer 2 is enabled.
Counter/Timer Select. This bit determines whether Timer 2 functions as a timer or counter.
Independent of this bit, Timer 2 runs at 2 clocks per tick when used in either baud-rate generator
or clock-output mode.
0 = Timer 2 function as a timer.
1 = Timer 2 counts negative transitions on the T2 pin (P1.0).
Capture/Reload Select. This bit determines whether the capture or reload function is used for
Timer 2. When set (= 1), Timer 2 captures occur when a falling edge is detected on T2EX(P1.1)
if EXEN2 = 1. When clear (= 0), Timer 2 functions in an autoreload mode. An autoreload occurs
following each overflow if RCLK or TCLK is set or if a falling edge is detected on T2EX if EXEN2 = 1.
0 = Autoreloads occur when Timer 2 overflows or a falling edge is detected on T2EX if EXEN2 = 1.
1 = Timer 2 captures occur when a falling edge is detected on T2EX if EXEN2 = 1.
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