XR17D152 Datasheet, PDF (16/68 Pages) Exar Corporation – UNIVERSAL (3.3V AND 5V) PCI BUS DUAL UART

XR17D152
UNIVERSAL (3.3V AND 5V) PCI BUS DUAL UART
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REV. 1.2.0
2.2.2 General Purpose 16-bit Timer/Counter. [TIMERMSB, TIMELSB, TIMER, TIMECNTL] (DEFAULT
0XXX-XX-00-00)
A 16-bit down-count timer for general purpose timer or counter. Its clock source may be selected from internal
crystal oscillator or externally on pin TMRCK. The timer can be set to be a single-shot for a one-time event or
re-triggerable for a continuous interval. An interrupt may be generated in the INT Register when the timer times
out. It is controlled through 4 configuration registers [TIMERCNTL, TIMER, TIMELSB, TIMERMSB]. These
registers provide start/stop and re-triggerable or one-shot operation. The time-out output of the Timer can be
set to generate an interrupt for system or event alarm.
FIGURE 7. TIMER/COUNTER CIRCUIT.
TIM ERM SB and TIM ERLSB
(16-bit Value)
TMRCK
1
OSC. CLOCK
0
1 6 -B it
Tim e-out
1
Tim er/C ounter
0
C lo ck
T IM E R C N T L [3] ^Select
S ta rt/S to p
TIM ERCNTL [1]
T IM E R C N T L [2 ] ^{Single/R e-triggerable}
R e-trigg er
0
1
S in g le -s h o t
T IM E R C N T L [0] ^{Tim er Interrupt Enable}
TIM ERCNTL [4]
Tim er Interrupt, C h-0 IN T=7
N o Interrupt
1
M PIO [0]
0
M PIO LVL[0]
TABLE 7: TIMER CONTROL REGISTERS
TIMERCNTL [0] Logic zero (default) disables Timer-Counter interrupt and logic one enables the interrupt, reading the
TIMERCNTL clears the interrupt.
TIMERCNLT [1] Logic zero (default) stops/pauses the timer and logic one starts/re-starts the timer/counter.
TIMERCNTL [2] Logic zero (default) selects re-trigger timer function and logic one selects one-shot (timer function.
TIMERCNTL [3] Logic zero (default) selects internal and logic one selects external clock to the timer/counter.
TIMERCNTL [4] Routes the Timer-Counter interrupt to MPIO[0] if MPIOSEL[0]=0 for external event control.
TIMERCNTL [7:5] Reserved (defaults to zero).
TIMER [15:8] Reserved
TIMERCNTL Register
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
Rsvd
Rsvd
Rsvd
M PIO [0]
C o n tro l
C lo c k
Select
Single/
R e -trig g e r
Start/
Stop
IN T
Enable
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