Datasheet CH9121 (Nanjing Qinheng Microelectronics) - 5

CH9121 Datasheet https://wch-ic.com powered on, it is forbidden to configure CH9121 through the host computer. In TCP mode, port 2 connection status indication output, low 33 TCPCS2 O level is valid. 36 RSTI I,PU External reset input, low level valid, built-in pull-up resistor. Transmitting status output, used to control the RS485 46 TNOW2 O transmitting and receiving switching of serial port 2. Transmitting status output, used to control the RS485 receiving 51 TNOW1 O and receiving switching of serial port 1. Carrier sensing indicator LED output: 52 ACT O LED flashes to indicate carrier sensing signal. Network connection indication LED output: 53 LINK O low level indicates that the Ethernet PHY is connected, high level indicates that the Ethernet PHY is not connected. 55 RXD2 I,PU Serial port 2 data input, built-in pull-up resistor. 56 TXD2 O Serial port 2 data output. 57 RXD1 I,PU Serial port 1 data input, built-in pull-up resistor. 58 TXD1 O Serial port 1 data output. Built-in pull-up resistor, if the detection pin is low for 2 seconds 59 RESET I,PU during power-on, CH9121 will be restored to factory settings Serial port configuration mode setting pin, built-in pull-up resistor, when a low level is detected, it enters the serial port 60 CFG I,PU configuration mode, and a high level exits the configuration mode. Note 1: I = Input; O = Output; I/O = Input/Output; P = Power; PU = Built-in pull-up resistor. V2.5 5 Document Outline 1. Overview 2. Features 3. Pinouts 4. Pin Definitions 5. Function Parameter Descriptions 5.1 Overview 5.2 Basic Parameters 5.3 Port Parameter 5.4 Default Configuration 6. Function Descriptions 6.1 UART 6.1.1 Serial Baud Rate 6.2 Other Hardware 7. Parameters 7.1 Absolute Maximum Value 7.2 Electrical Parameters 7.3 Power Consumption 7.4 AC Electrical Characteristics and Timing 8. Package Information 8.1 TSSOP20 8.2 LQFP64M 9. Applications 9.1 CH9121T Reference Circuit 9.2 CH9121A Reference Circuit