XR16M598 Datasheet, PDF (28/58 Pages) Exar Corporation – 1.62V TO 3.63V HIGH PERFORMANCE OCTAL UART WITH 16-BYTE FIFO

XR16M598
1.62V TO 3.63V HIGH PERFORMANCE OCTAL UART WITH 16-BYTE FIFO
REV. 1.0.0
TABLE 11: TIMER CONTROL COMMANDS
TIMERCNTL [7:4] Reserved
TIMERCNTL [3:0]
These bits are used to invoke a series of commands that control the function of the Timer/Counter.
The commands 1011 to 1111 are reserved.
0001: Enable Timer Interrupt
0010: Disable Timer Interrupt (default)
0011: Select One-shot mode
0100: Select Re-triggerable mode (default)
0101: Select Internal Crystal Oscillator output as clock source for the Timer (default)
0110: Select External Clock source (through TMRCK pin) for the Timer
0111: Reserved
1000: Reserved
1001: Start Timer
1010: Stop Timer (default)
1011: Reset Timer
Upon power-up or reset, the default states are Timer interrupt disabled, Re-triggerable mode, Crystal
Oscillator as Timer clock source, and Timer stopped.
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
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