SC16IS741IPW,128 NXP Semiconductors, SC16IS741IPW,128 Datasheet - Page 30

• Manufacturer Part Number: SC16IS741IPW,128
• Description: IC UART 16TSSOP
• Manufacturer: NXP Semiconductors
• Type: IrDA or RS-232 or RS-485r

Specifications of SC16IS741IPW,128

• Number Of Channels: 1, UART
• Package / Case: 16-TSSOP (0.173", 4.40mm Width)
• Features: RS-485
• Fifo's: 64 Byte
• Protocol: RS232, RS485
• Voltage - Supply: 2.5V, 3.3V
• With Auto Flow Control: Yes
• With Irda Encoder/decoder: Yes
• With False Start Bit Detection: Yes
• With Modem Control: Yes
• Mounting Type: Surface Mount
• Data Rate: 5 Mbps
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 2.3 V
• Supply Current: 6 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 2.5 V, 3.3 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 935290736128

NXP Semiconductors
9. RS-485 features
SC16IS741_1
Product data sheet
9.3.1 Normal multidrop mode
9.1 Auto RS-485 RTS control
9.2 RS-485 RTS output inversion
9.3 Auto RS-485
Normally the RTS pin is controlled by MCR bit 1, or if hardware flow control is enabled, the
logic state of the RTS pin is controlled by the hardware flow control circuitry. EFCR
register bit 4 will take the precedence over the other two modes; once this bit is set, the
transmitter will control the state of the RTS pin. The transmitter automatically asserts the
RTS pin (logic 0) once the host writes data to the transmit FIFO, and deasserts RTS pin
(logic 1) once the last bit of the data has been transmitted.
To use the auto RS-485 RTS mode the software would have to disable the hardware flow
control function.
EFCR bit 5 reverses the polarity of the RTS pin if the UART is in auto RS-485 RTS mode.
When the transmitter has data to be sent it will deasserts the RTS pin (logic 1), and when
the last bit of the data has been sent out the transmitter asserts the RTS pin (logic 0).
EFCR bit 0 is used to enable the RS-485 mode (multidrop or 9-bit mode). In this mode of
operation, a ‘master’ station transmits an address character followed by data characters
for the addressed ‘slave’ stations. The slave stations examine the received data and
interrupt the controller if the received character is an address character (parity bit = 1).
To use the auto RS-485 mode the software would have to disable the hardware and
software flow control functions.
The 9-bit Mode in EFCR (bit 0) is enabled, but not Special Character Detect (EFR bit 5).
The receiver is set to Force Parity 0 (LCR[5:3] = 111) in order to detect address bytes.
With the receiver initially disabled, it ignores all the data bytes (parity bit = 0) until an
address byte is received (parity bit = 1). This address byte will cause the UART to set the
parity error. The UART will generate a line status interrupt (IER bit 2 must be set to ‘1’ at
this time), and at the same time puts this address byte in the RX FIFO. After the controller
examines the byte it must make a decision whether or not to enable the receiver; it should
enable the receiver if the address byte addresses its ID address, and must not enable the
receiver if the address byte does not address its ID address.
If the controller enables the receiver, the receiver will receive the subsequent data until
being disabled by the controller after the controller has received a complete message
from the ‘master’ station. If the controller does not disable the receiver after receiving a
message from the ‘master’ station, the receiver will generate a parity error upon receiving
another address byte. The controller then determines if the address byte addresses its ID
address, if it is not, the controller then can disable the receiver. If the address byte
addresses the ‘slave’ ID address, the controller take no further action, the receiver will
receive the subsequent data.
Single UART with I
Rev. 01 — 29 April 2010
2
C-bus/SPI interface, 64-byte FIFOs, IrDA SIR
SC16IS741
© NXP B.V. 2010. All rights reserved.
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