Serial port expansion

灞波儿奔

Serial port expansion [Copy link]

I found a broken circuit board under the table and saw a chip GM8125. The main function of this chip is to expand the serial port.

GM8125 can expand a full-duplex standard serial port into 5 standard serial ports, and can control the serial port expansion mode through external pins: single-channel working mode and multi-channel working mode, that is, you can specify a sub-serial port and the mother serial port to work at the same baud rate, or you can let all the sub-serial ports work simultaneously based on the mother serial port baud rate.
When the chip works in multi-channel mode, the sub-serial port can actively respond to the data sent by the slave, and send it to the host by the mother serial port, and return the sub-serial port address at the same time. This mode enables each slave's sending request to be responded to in a timely manner. Even if all slaves have a sending request at the same time, the data will not be lost, and the real-time communication between the main control unit and the peripherals is basically realized. The
working baud rate of the mother and sub-serial ports of the chip can be adjusted by software without modifying the external circuit and crystal frequency. The chip has less external control, flexible application, simple programming and use, and is suitable for most systems with serial port expansion requirements.

2 Features
——Control the chip by writing control words ——Baud rate of each slave serial port is adjustable (unified adjustment) ——Data format 10 bits or 11 bits optional
——In single-channel mode, the highest baud rate supports 20Mbps; in multi-channel mode, the highest baud rate of the slave serial port is 38400bps ——Number of slave serial ports: 5
——A pin selects whether the chip works in single-channel mode or multi-channel mode
——In single-channel mode, the chip does not need to be initialized, and the working serial port is selected by the address line ——In multi-channel mode, the baud rate of each slave serial port is equal to 6 of the baud rate of the mother serial port ——In multi-channel mode, when receiving, the address lines SRADD2~0 return the address of the receiving sub-channel to the MCU.
After the MCU receives the data sent from the mother serial port, it can determine which slave serial port the data is sent from according to the SRADD2~0 status; when sending, the MCU first selects the slave serial port and then sends data to the mother serial port ——Compatible with standard serial port communication format, TTL level output ——Wide operating voltage: 2.3~6.7V
——Output baud rate error is less than 0.2%, input baud rate error is required to be less than 2.8% ——Sampling 16 times per bit to improve data accuracy
——Input address pins have 50~80KΩ Pull-Down resistors, other input pins have 50~80KΩ Pull-Up resistors
(except OSCI)

alan000345

Thanks for sharing.