XR16V794 Datasheet, PDF (22/53 Pages) Exar Corporation – HIGH PERFORMANCE 2.25V TO 3.6V QUAD UART WITH FRACTIONAL

XR16V794
HIGH PERFORMANCE 2.25V TO 3.6V QUAD UART WITH FRACTIONAL BAUD RATE
REV. 1.0.0
3.1.2 General Purpose 16-bit Timer/Counter [TIMERMSB, TIMELSB, TIMER, TIMECNTL] (DEFAULT
0XXX-XX-00-00)
The 794 includes a 16-bit general purpose timer/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 periodic signal. An interrupt may be generated when the timer times out and will show up as a
Channel 0 interrupt (see Table 9). It is controlled through 4 configuration registers [TIMERCNTL, TIMER,
TIMELSB, TIMERMSB]. These registers provide start/stop and re-triggerable or one-shot operation (see
Table 10 below). The time-out output of the Timer can be set to generate an interrupt for system or event
alarm.
3.1.2.1 TIMERMSB [7:0] and TIMERLSB [7:0]
TIMERMSB and TIMERLSB form a 16-bit value. The least-significant bit of the timer is being bit-0 of the
TIMERLSB with most-significant-bit being bit-7 in TIMERMSB. Notice that these registers do not hold the
current counter value when read. Default value is zero (timer disabled) upon powerup and reset.
16-Bit Timer/Counter Programmable Registers
TIMERMSB Register
TIMERLSB Register
Bit-15 Bit-14 Bit-13 Bit-12 Bit-11 Bit-10 Bit-9 Bit-8
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
3.1.2.2 TIMER [7:0] Reserved
3.1.2.3 TIMERCNTL [7:0] Register
The bits 3:0 of this register are used to issue commands. The commands are self-clearing, so reading this
register does not show the last written command. Reading this register returns a value of 0x01 when there is a
Timer interrupt pending and 0x00 at all other times.
TABLE 10: 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
0011: Select One-shot mode
0100: Select Re-triggerable mode
0101: Select Internal Crystal Oscillator output as clock source for the Timer
0110: Select External Clock source (through TMRCK pin) for the Timer
0111: Reserved
1000: Reserved
1001: Start Timer
1010: Stop Timer
1011: Reset Timer
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