XR16M752 Datasheet, PDF (19/51 Pages) Exar Corporation – HIGH PERFORMANCE DUART WITH 64-BYTE FIFO

REV. 1.0.2
XR16M752/XR68M752
HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
FIGURE 11. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING
Character
Data Bits
TX Data ^{0 1 0 1 0 0 1 1 0 1}
Transmit
IR Pulse
(TX Pin)
Receive
IR Pulse
(RX pin)
Bit Time
3/16 Bit Time
Bit Time
1/16 Clock Delay
1/2 Bit Time
IrEncoder-1
RX Data
0 1 0 1 0 0 11 0 1
Data Bits
Character
IRdecoder-
2.18 Sleep Mode with Auto Wake-Up
The M752 supports low voltage system designs, hence, a sleep mode is included to reduce its power
consumption when the chip is not actively used.
All of these conditions must be satisfied for the M752 to enter sleep mode:
■ no interrupts pending for both channels of the M752 (ISR bit-0 = 1)
■ sleep mode of both channels are enabled (IER bit-4 = 1)
■ modem inputs are not toggling (MSR bits 0-3 = 0)
■ RX input pins are idling HIGH
The M752 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 M752 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 M752 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 M752 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
an interrupt is pending from channel A or B. The M752 will stay in the sleep mode of operation until it is
disabled by setting IER bit-4 to a logic 0.
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