XR16M781IL32-F Datasheet, PDF (20/52 Pages) Exar Corporation – 1.62V TO 3.63V UART WITH 64-BYTE FIFO AND VLIO INTERFACE

XR16M781
1.62V TO 3.63V UART WITH 64-BYTE FIFO AND VLIO INTERFACE
FIGURE 13. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING
REV. 1.0.1
Character
Data Bits
TX Data 0 ¹ 0 ¹ 0 0 ^{1 1} 0 ¹
Transmit
IR Pulse
(TX Pin)
Bit Time _{3/16 or 1/4 Bit Time}
1/2 Bit Time
IrEncoder-1
Receive
IR Pulse
(RX pin)
RX Data
Bit Time
1/16 Clock Delay
0 1 0 1 0 0 11 0 1
Data Bits
Character
IRdecoder-1
2.17 Sleep Mode with Auto Wake-Up and Power-Save feature
The M781 supports low voltage system designs, hence, a sleep mode with auto wake-up and power-save
feature is included to reduce its power consumption when the chip is not actively used.
2.17.1 Sleep mode
All of these conditions must be satisfied for the M781 to enter sleep mode:
■ no interrupts pending (ISR bit-0 = 1)
■ sleep mode is enabled (IER bit-4 = 1)
■ modem inputs are not toggling (MSR bits 0-3 = 0)
■ RX input pin is idling HIGH in normal mode or LOW in infrared mode
■ divisor is non-zero
■ TX and RX FIFOs are empty
The M781 stops its crystal oscillator to conserve power in the sleep mode. User can check the XTAL2 pin for
no clock output as an indication that the device has entered the sleep mode.
The M781 resumes normal operation by any of the following:
■ a receive data start bit transition (HIGH to LOW)
■ a data byte is loaded to the transmitter, THR or FIFO
■ a change of logic state on any of the modem or general purpose serial inputs: CTS#, DSR#, CD#, RI#
If the M781 is awakened by any one of the above conditions, it will return to the sleep mode automatically after
all interrupting conditions have been serviced and cleared. If the M781 is awakened by the modem inputs, a
read to the MSR is required to reset the modem inputs. In any case, the sleep mode will not be entered while
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