The DataSheet of CH341 (the first)

8

07H~06H

PID

Product ID, high byte is behind, any value

55??H

09H~08H

RID

Release ID, high byte is behind, any value

0100H

17H~10H

SN

Serial number, the size is 8

12345678

DID

Printer port: defined printer device ID string accord IEEE-1284

7FH~20H

PIDS

Serial interface or printer port: production explanation string of

un-printer

00H, 00H

Others

(Reserved unit)

00H or FFH

The following table is CFG defining detail configuration, explanation is according bit.

Bit

address

Shortened

form

Explanation

Default value

7

PRT

Select communication interface: for serial interface, the value

must be 1

For un-serial interface select: 0=standard USB printer port;

1=parallel interface

1

6

PWR

USB device supply power mode: 0=peripheral and USB;

1=USB bus only

1

5

SN-S

Production serial number string: 0=valid; 1=invalid

1

DID-S

Printer’s device ID string:0=valid; 1=invalid

1

4

PID-S

Product explanation string of un-printer: 0=valid; 1=invalid

1

3

SPD

Data transfer speed of printer port:0=high-speed;

1=low-speed/standard

1

2

SUSP

Automatically suspend and low-cost when USB is not busy,

0=forbid; 1=allow

1

1

0

PROT

Define interface protocol in configuration description sign of

USB device: for serial or parallel interface, the valid value is

0 to 3, 0 is recommended,

For standard USB printer port: the valid value is 1 and 2, 2 is

recommended

1

0

5.4.Asynchronous serial interface

In the asynchronous serial mode the CH341’s pins contain: data transfer pin, hardware speed control

pin, operation state pin, MODEM communication signal pin and assistant pin.

Data transfer pin consists: TXD and RXD pins. When serial interface is leisure TXD and RXD are

high-level.

Hardware speed control pin consists: TEN# and RDY#. TEN# is serial interface transfer enable, when it

is high-level, CH341 will stop transfer data from serial interface. Until it is low-level, CH341 will go on

transferring data. RDY# is serial interface receive ready. When it is high-level indicate CH341 is not ready

to receive data, maybe the chip is reset, USB is un-configure, cancel configuration or serial interface receive

buffer is full etc.

Operation state pins consist: TNOW and ROV# pins. TNOW with high-level indicates CH341 is

transferring data from serial interface. When the transfer is completed the TNOW is low-level. TNOW can

indicate serial interface receive and transfer switch state in semi-duplex serial interface mode. ROV#

indicates CH341 internal serial interface receive buffer will overflow or have overflowed and the following

data will discard. In common, the receive buffer is not overflow, so the ROV# is high-level.

MODEM communicate signal pins consist: CTS#, DSR#, RI#, DCD# , DTR# and RST# pin. All the

MODEM communication signals are controlled and defined by computer applied program, not directly