Introduction
CH340 is a USB bus convert chip and it can realize USB convert to serial interface, USB convert to
IrDA infrared or USB convert to printer interface.
In serial interface mode, CH340 supplies common MODEM liaison signal, used to enlarge
asynchronous serial interface of computer or upgrade the common serial device to USB bus directly. More
detail about USB convert to printer interface please referring to the second manual CH340DS2.
In infrared mode, add infrared transceiver to CH340 can compose USB infrared adapter, realize SIR
infrared communication.
Features
? Full speed USB device interface, conforms to USB Specification Version 2.0, only needs crystal and
capacitance external.
? Emulate standard serial interface, used to upgrade the former peripheral device, or add excess serial
interface through USB.
? Totally compatible with serial application program in computer endpoint Windows operation system.
? Hardware full duplex serial interface, set transceiver buffer, supports communication baud rate varies
from 50bps to 2Mbps.
? Supports common MODEM liaison signal RTS, DTR, DCD, RI, DSR and CTS.
? Through adding level converter equipment to supply RS232, RS485, RS422 and other interface.
? Supports IrDA criterion SIR infrared communication, supports baud rate varies from 2400bps to
115200bps.
? For it is through USB converts to serial interface, only compatible with application layer not totally.
? Software compatible with CH341, using drive of CH341 directly.
? Support 5V and 3.3V source voltage.
? Supply SSOP-20 package without lead, compatible with RoHS.
Function description
CH340 chip set up USB pull-up resistor internal, UD+ and UD- pins must be connected to USB bus
directly.
CH340 chip set up power up reset circuit internal.
When CH340 chip is working normally, the outside must supply 12MHz clock signal to XI pin. In
generally, clock signal is generated by inverter in CH340 through oscillating of crystal keeping frequency. A
crystal of 12MHz between XI and XO, XI and XO connect a high frequency oscillator capacitance to ground
respectively can compose the peripheral circuit.
CH340 chip supports 5V and 3.3V power voltage. When using 5V source power, the VCC input 5V
power and the pin of V3 must connect with 4700pF or 0.01uF decoupling capacitance. When using 3.3V
power voltage, connects V3 with VCC, and input 3.3V power voltage. And the other circuit voltage which is
connected with CH340 is no more than 3.3V.
CH340 automatically supports USB device suspending to save power consume. NOS# is low–level can
forbid USB device suspending.
In asynchronous serial interface mode, CH340 chip contains these pins: data transfer pin, MODEM
liaison signal pin and assistant pin.
Data transfer pin contains: TXD pin and RXD pin. When serial interface is idle, RXD must be
high-level. If R232 is high-level, use assistant RS232 function, then RXD pin automatically inserts a inverter
internal, and low-level is in default. When serial interface output is free, the TXD in CH340H and CH340T
is high level, TXD in CH340R is low-level.
MODEM liaison signal pin contains: CTS#, DSR#, RI#, DCD# and RTS#. All these MODEM liaison
signal are controlled by computer application program and application program defines function.
Assistant pin contains: IR#, R232, CKOH, CKOL and ACT#. When IR# is low-level, starts infrared
serial interface mode. R232 is used to control assistant RS232 function. When R232 is high-level, RXD pin
automatically insert a inverter internal, and output opposite phase clock from CKOH and CKOL. ACT# is
USB device configuration finished state output (such as USB infrared adapter is ready) when R232 is
low-level. IR# and R232 only be detected once a time after power reset.
CH340 set separate transceiver buffer internal and supports simplex, semiduplex and full duplex
asynchronous serial communication. Serial data contains one low-level start bit , eight or nine data bit and
The DataSheet of CH340 (the first) 4
one high-level stop bit. Supporting odd check/even check/flag check/blank check. CH340 supports common
baud rate: 50,75,100,110,134.5,150,300,600,900,1200,1800,2400,3600,4800,9600,14400,19200,28800,
33600,38400, 56000,57600,76800,115200,128000,153600,230400,460800,921600,1500000,2000000 and so
on. The baud rate error of serial transfer signal is less than 0.3%, and permission baud rate error of serial
receive signal is not less than 0.2%.
In the WINDOWS operation system of computer endpoint, drive program of CH340 can communicate
standard serial interface. So the mostly original serial interface application program is totally compatible,
and without any modify.
CH340 can be used to upgrade the former serial interface peripheral equipment, or add extra serial
interface for computer via USB bus. Supply RS232, RS485, RS422 and other interface via adding level
change device.
Only add infrared transceiver, CH340 can add SIR infrared adapter for computer via USB bus, realize
infrared communication between computer and peripheral equipment which is according to IrDA criterion.
CH340 is a USB bus convert chip and it can realize USB convert to serial interface, USB convert to
IrDA infrared or USB convert to printer interface.
In serial interface mode, CH340 supplies common MODEM liaison signal, used to enlarge
asynchronous serial interface of computer or upgrade the common serial device to USB bus directly. More
detail about USB convert to printer interface please referring to the second manual CH340DS2.
In infrared mode, add infrared transceiver to CH340 can compose USB infrared adapter, realize SIR
infrared communication.
Features
? Full speed USB device interface, conforms to USB Specification Version 2.0, only needs crystal and
capacitance external.
? Emulate standard serial interface, used to upgrade the former peripheral device, or add excess serial
interface through USB.
? Totally compatible with serial application program in computer endpoint Windows operation system.
? Hardware full duplex serial interface, set transceiver buffer, supports communication baud rate varies
from 50bps to 2Mbps.
? Supports common MODEM liaison signal RTS, DTR, DCD, RI, DSR and CTS.
? Through adding level converter equipment to supply RS232, RS485, RS422 and other interface.
? Supports IrDA criterion SIR infrared communication, supports baud rate varies from 2400bps to
115200bps.
? For it is through USB converts to serial interface, only compatible with application layer not totally.
? Software compatible with CH341, using drive of CH341 directly.
? Support 5V and 3.3V source voltage.
? Supply SSOP-20 package without lead, compatible with RoHS.
Function description
CH340 chip set up USB pull-up resistor internal, UD+ and UD- pins must be connected to USB bus
directly.
CH340 chip set up power up reset circuit internal.
When CH340 chip is working normally, the outside must supply 12MHz clock signal to XI pin. In
generally, clock signal is generated by inverter in CH340 through oscillating of crystal keeping frequency. A
crystal of 12MHz between XI and XO, XI and XO connect a high frequency oscillator capacitance to ground
respectively can compose the peripheral circuit.
CH340 chip supports 5V and 3.3V power voltage. When using 5V source power, the VCC input 5V
power and the pin of V3 must connect with 4700pF or 0.01uF decoupling capacitance. When using 3.3V
power voltage, connects V3 with VCC, and input 3.3V power voltage. And the other circuit voltage which is
connected with CH340 is no more than 3.3V.
CH340 automatically supports USB device suspending to save power consume. NOS# is low–level can
forbid USB device suspending.
In asynchronous serial interface mode, CH340 chip contains these pins: data transfer pin, MODEM
liaison signal pin and assistant pin.
Data transfer pin contains: TXD pin and RXD pin. When serial interface is idle, RXD must be
high-level. If R232 is high-level, use assistant RS232 function, then RXD pin automatically inserts a inverter
internal, and low-level is in default. When serial interface output is free, the TXD in CH340H and CH340T
is high level, TXD in CH340R is low-level.
MODEM liaison signal pin contains: CTS#, DSR#, RI#, DCD# and RTS#. All these MODEM liaison
signal are controlled by computer application program and application program defines function.
Assistant pin contains: IR#, R232, CKOH, CKOL and ACT#. When IR# is low-level, starts infrared
serial interface mode. R232 is used to control assistant RS232 function. When R232 is high-level, RXD pin
automatically insert a inverter internal, and output opposite phase clock from CKOH and CKOL. ACT# is
USB device configuration finished state output (such as USB infrared adapter is ready) when R232 is
low-level. IR# and R232 only be detected once a time after power reset.
CH340 set separate transceiver buffer internal and supports simplex, semiduplex and full duplex
asynchronous serial communication. Serial data contains one low-level start bit , eight or nine data bit and
The DataSheet of CH340 (the first) 4
one high-level stop bit. Supporting odd check/even check/flag check/blank check. CH340 supports common
baud rate: 50,75,100,110,134.5,150,300,600,900,1200,1800,2400,3600,4800,9600,14400,19200,28800,
33600,38400, 56000,57600,76800,115200,128000,153600,230400,460800,921600,1500000,2000000 and so
on. The baud rate error of serial transfer signal is less than 0.3%, and permission baud rate error of serial
receive signal is not less than 0.2%.
In the WINDOWS operation system of computer endpoint, drive program of CH340 can communicate
standard serial interface. So the mostly original serial interface application program is totally compatible,
and without any modify.
CH340 can be used to upgrade the former serial interface peripheral equipment, or add extra serial
interface for computer via USB bus. Supply RS232, RS485, RS422 and other interface via adding level
change device.
Only add infrared transceiver, CH340 can add SIR infrared adapter for computer via USB bus, realize
infrared communication between computer and peripheral equipment which is according to IrDA criterion.
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