XR16V798_08 Datasheet, PDF (25/56 Pages) Exar Corporation – HIGH PERFORMANCE 2.25V TO 3.6V OCTAL UART WITH FRACTIONAL

XR16V798
REV. 1.0.1
HIGH PERFORMANCE 2.25V TO 3.6V OCTAL UART WITH FRACTIONAL BAUD RATE
TIMER OPERATION
The following paragraphs describe the operation of the 16-bit Timer/Counter. The following conventions will be
used in this discussion:
■ ’N’ is the 16-bit value programmed in the TIMER MSB, LSB registers
■ ‘N’ can take any value from 0x0002 to 0xFFFF.
Timer Interrupt
In the one-shot mode, the Timer will issue an interrupt ’N’ clocks after the Timer is started. This is the time
when the Timer times-out in the one-shot mode. In the re-triggerable mode, the Timer will keep issuing an
interrupt every ’N’ clocks. This is shown in Figure 15, where the time between successive time-outs (in re-
triggereble mode) is ’N’ clocks. The Timer interrupt can be cleared by reading the TIMERCNTL register. The
TIMERCNTL will read a value of 0x01 when there is an interrupt and a 0x00 at all other times.
FIGURE 14. TIMER/COUNTER CIRCUIT.
TIMERMSB and TIMERLSB
(16-bit Value)
TMRCK
1
OSC. CLOCK
0
Timer Interrupt
1
16-Bit
0
Timer/Counter
Clock Select
Start/Stop
TIMERCNTL
COMMANDS ^{Single shot/Re-triggerable}
Timer Interrupt Enable/ Disable
Timer Interrupt
No Interrupt
FIGURE 15. INTERRUPT OUTPUT IN ONE-SHOT AND RE-TRIGGERABLE MODES
Timer Started
Timer Timed
Out
TIMERCNTL
read
One-shot Mode
Re-triggerable
Mode
Timer Timed TIMERCNTL Timer Timed
Out
read
Out
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