xr16m670 Exar Corporation, xr16m670 Datasheet - Page 20

• Manufacturer Part Number: xr16m670
• Description: 1.62v To 3.63v High Performance Uart With 32-byte Fifo
• Manufacturer: Exar Corporation

XR16M670
1.62V TO 3.63V HIGH PERFORMANCE UART WITH 32-BYTE FIFO
The M670 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.
All of these conditions must be satisfied for the M670 to enter sleep mode:
The M670 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 M670 resumes normal operation by any of the following:
If the M670 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 M670 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
F
2.17
2.17.1
IGURE
■
■
■
■
■
■
■
■
■
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
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#
13. I
Sleep Mode with Auto Wake-Up and Power-Save feature
Sleep mode
NFRARED
T
RANSMIT
TX Data
Transmit
(TX Pin)
IR Pulse
Receive
IR Pulse
(RX pin)
RX Data
D
ATA
0
E
NCODING AND
Bit Time
Bit Time
0
1
1/16 Clock Delay
1
0
0
3/16 or 1/4 Bit Time
1
Character
Data Bits
1
R
20
Data Bits
Character
0
ECEIVE
0
0
0
D
1
ATA
1
1
D
1
ECODING
0
0
1
1/2 Bit Time
1
IRdecoder-1
IrEncoder-1
REV. 1.0.0