XR16C864 Datasheet, PDF (19/51 Pages) Exar Corporation – 2.97V TO 5.5V QUAD UART WITH 128-BYTE FIFO

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REV. 2.0.1
XR16C864
2.97V TO 5.5V QUAD UART WITH 128-BYTE FIFO
infrared modules on the market which indicate a logic 0 by a light pulse. So the 864 has a provision to invert
the input polarity to accomodate this. In this case, user can enable FCTR bit-2 to invert the input signal.
FIGURE 11. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING
C h a ra cte r
Data Bits
TX Data ^{0 1 0 1 0 0 1 1 0 1}
Transm it
IR Pulse
(TX Pin)
Bit Tim e
3/16 Bit Tim e
1/2 Bit Tim e
IrEncoder-1
Receive
IR Pulse
(RX pin)
Bit Time
1/16 Clock Delay
RX Data
0 1 0 1 0 0 11 0 1
Data Bits
Character
IRdecoder-1
2.21 Sleep Mode with Auto Wake-Up
The 864 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 864 to enter sleep mode:
s no interrupts pending for all four channels of the 864 (ISR bit-0 = 1)
s sleep mode of all four channels are enabled (IER bit-4 = 1)
s modem inputs are not toggling (MSR bits 0-3 = 0)
s RX input pins are idling at a logic 1
The 864 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 864 resumes normal operation by any of the following:
s a receive data start bit transition (logic 1 to 0)
s a data byte is loaded to the transmitter, THR or FIFO
s a change of logic state on any of the modem or general purpose serial inputs: CTS#, DSR#, CD#, RI#
If the 864 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 864 is awakened by the modem inputs, a read
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