DS87C550 High-Speed Microcontroller User’s Guide Supplement
34 of 93
TR2
Bit 2
Timer 2 Run Control.
This bit enables/disables the operation of timer 2. Halting
this timer will preserve the current count in TH2, TL2.
0 = Timer 2 is halted.
1 = Timer 2 is enabled.
2
T
/
C
Bit 1
Counter/Timer Select.
This bit determines whether timer 2 will function 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. The speed of timer 2 is determined by the T2M
bit (CKCON.5).
1 = Timer 2 will count negative transitions on the T2 pin.
2
RL
Bit 0
Reload Enable.
This bit determines if the reload function will be used for timer
2. If either RCLK or TCLK is set, this bit will not function and the timer will
function in an auto-reload mode following each overflow.
0 = Auto-reloads will occur when timer 2 overflows or a falling edge is detected
on T2EX if EXEN2=1.
1 = Timer 2 reload function is disabled.
Timer 2 Mode (T2MOD)
7
6
5
4
3
2
1
0
SFR BFh
-
-
-
-
-
-
T2OE
DCEN
RW-0
RW-0
R=Unrestricted Read, W=Unrestricted Write, -n=Value after Reset
Bits 7-2
Reserved. Read data will be indeterminate.
T2OE
Bit 1
Timer 2 Output Enable.
This bit enables/disables the clock output function of
the T2 pin.
0 = The T2 pin functions as either a standard port pin or as a counter input for
timer 2.
1 = Timer 2 will drive the T2 pin with a clock output if C/T2=0. Also, timer 2
rollovers will not cause interrupts in this case.
DCEN
Bit 0
Down Count Enable.
This bit, in conjunction with the T2EX pin, controls the
direction that timer 2 counts in 16-bit auto-reload mode.
DCEN
T2EX
DIRECTION
1
1
Up
1
0
Down
0
X
Up