Description
GE DS2020ACHAG1 module
Contact: Mr. Lai
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Analysis of PLC”s most basic serial communication
When using PLC, electric power operators will be exposed to many communication protocols and communication interfaces. Do you know the most basic PLC serial communication and basic communication interfaces?
Serial port is a very general device communication protocol on the computer (don”t confuse it with Universal Serial Bus or USB). Most computers contain two serial ports based on RS232. The serial port is also a common communication protocol for instruments and meters; Many GPIB compatible devices also have RS-232 ports. At the same time, the serial communication protocol can also be used to obtain data from remote acquisition equipment.
Serial communication is completed with three wires: (1) ground wire, (2) transmission, and (3) reception. Because serial communication is asynchronous, the port can send data on one line and receive data on another line. Other lines are used to shake hands, but are not necessary.
The most important parameters of serial communication are baud rate, data bit, stop bit and parity. For two ports to pass, these parameters must match:
a. Baud rate: This is a parameter to measure the communication speed. It represents the number of bits transmitted per second. For example, 300 baud means sending 300 bits per second. When we mention the clock cycle, we mean the baud rate. For example, if the protocol requires 4800 baud rate, the clock is 4800Hz. This means that the sampling rate of serial communication on the data line is 4800Hz. Generally, the baud rate of the telephone line is 1440028800 and 36600. The baud rate can be much larger than these values, but the baud rate is inversely proportional to the distance. The high baud rate is often used for communication between closely placed instruments.
b. Data bit: This is a parameter to GE DS2020ACHAG1 measure the actual data bit in communication. When the computer sends a packet, the actual data will not be 8 bits, and the standard values are 5, 7 and 8 bits. How to set depends on the information you want to send. For example, the standard ASCII code is 0~127 (7 bits). The extended ASCII code is 0 to 255 (8 bits). If the data uses simple text (standard ASCII code), then each packet uses 7-bit data. Each packet refers to a byte, including start/stop bit, data bit and parity bit. Since the actual data bit depends on the choice of communication protocol, the term “packet” refers to any communication situation.
c. Stop bit: used to represent the last bit of a single package. Typical values are 1, 1.5 and 2 bits. Because the data is timed on the transmission line, and each device has its own clock, it is likely that there is a small unsynchronization between the two devices in the communication. Therefore, the stop bit not only indicates the end of transmission, but also provides an opportunity for the computer to correct clock synchronization. The more bits applicable to the stop bit, the greater the tolerance of different clock synchronization, but the slower the data transmission rate.
d. Parity bit: a simple error detection method in serial communication. There are four error detection methods: even, odd, high and low. Of course, there is no check bit. In the case of even and odd parity, the serial port will set the parity bit (the bit after the data bit), and use a value to ensure that the transmitted data has even or odd logical high bits. For example, if the data is 011, for even parity, the check bit is 0, and the number of digits with high logic is even. If it is odd check, check bit 1, so there are three logical high bits. The high and low bits do not really check the data. Simply set the logic high or low to check. In this way, the receiving device can know the status of a bit and have the opportunity to judge whether there is noise interfering with communication or the data transmitted and received are not synchronized.
a. What is RS-232?
RS-232 (ANSI/EIA-232 standard) is the serial connection standard on IBM-PC and its compatible computers. It can be used for many purposes, such as connecting a mouse, printer or Modem, and also connecting industrial instruments and meters. For the improvement of drive and connection, the transmission length or speed of RS-232 often exceeds the standard value in practical applications.
RS-232 is only limited to point-to-point communication between PC serial port and equipment. The maximum distance of RS-232 serial communication is 50 feet.
b. What is RS-422?
RS-422 (EIARS-422-AS Standard) is the serial port connection standard of Apple”s Macintosh computer.
RS-422 uses differential signal and RS-232 uses signal of unbalanced reference ground. Differential transmission uses two lines to send and receive signals. Compared with RS-232, it can better resist noise and have a longer transmission distance. Better noise resistance and longer transmission distance are great advantages in industrial environment.
c. What is RS-485?
RS-485 (EIA-485 standard) is an improvement of RS-422 because it increases the number of devices from 10 to 32, and defines the electrical characteristics under the maximum number of devices to ensure sufficient signal voltage. With the ability of multiple devices, you can use a single RS-422 port to establish a device network. Excellent anti-noise and multi-device capability. RS-485 will be selected for serial connection when establishing distributed device network connected to PC, other data collection controllers, HMI or other operations in industrial applications.
RS-485 is a superset of RS-422, so all RS-422 devices can be controlled by RS-485. RS-485 can use more than 4000 feet of cable for serial communication.
IS420UCPAH2A
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Company advantage service:
1.Has been engaged in industrial control industry for a long time, with a large number of inventories.
2.Industry leading, price advantage, quality assurance
3.Diversified models and products, and all kinds of rare and discontinued products
4.15 days free replacement for quality problems
1.Has been engaged in industrial control industry for a long time, with a large number of inventories.
2.Industry leading, price advantage, quality assurance
3.Diversified models and products, and all kinds of rare and discontinued products
4.15 days free replacement for quality problems
All kinds of module card driver controller servo motor servo motor embedded card wires and cables Power module control module is applicable to steel, hydropower, nuclear power, power generation, glass factory, tire factory, rubber, thermal power, paper making, shipping, navigation, etc
ABB — AC 800M controller, Bailey, PM866 controller, IGCT silicon controlled 5SHY 3BHB01 3BHE00 3HNA00 DSQC series
BENTLY — 3500 system/proximitor, front and rear card, sensor, probe, cable 3500/20 3500/61 3500/05-01-02-00-001 3500/40M 176449-01 3500/22M 138607-01
Emerson — modbus card, power panel, controller, power supply, base, power module, switch 1C31,5X00, CE400, A6500-UM, SE3008,1B300,1X00,
EPRO — PR6423 PR6424 PR6425 PR6426 PR9376 PR9268 Data acquisition module, probe, speed sensor, vibration sensor
FOXBORO — FCP270 FCP280 FCM10EF FBM207 P0914TD CP40B FBI10E FBM02 FBM202 FBM207B P0400HE Thermal resistance input/output module, power module, communication module, cable, controller, switch
GE —- IS200/215/220/230/420 DS200/215 IC693/695/697/698 VMICPCI VMIVME 369-HI-R-M-0-0-E 469 module, air switch, I/O module, display, CPU module, power module, converter, CPU board, Ethernet module, integrated protection device, power module, gas turbine card
HIMA — F3 AIO 8/4 01 F3231 F8627X Z7116 F8621A 984862160 F3236 F6217 F7553 DI module, processor module, AI card, pulse encoder
Honeywell — Secure digital output card, program module, analog input card, CPU module, FIM card
MOOG — D136-001-007 Servo valve, controller, module
NI — SCXI-1100 PCI – PXIE – PCIE – SBRIO – CFP-AO-210 USB-6525 Information Acquisition Card, PXI Module, Card
Westinghouse — RTD thermal resistance input module, AI/AO/DI/DO module, power module, control module, base module
Woodward — 9907-164 5466-258 8200-1300 9907-149 9907-838 EASYGEN-3500-5/P2 8440-2145 Regulator, module, controller, governor
YOKOGAWA – Servo module, control cabinet node unit
Main products:
PLC, DCS, CPU module, communication module, input/output module (AI/AO/DI/DO), power module, silicon controlled module, terminal module, PXI module, servo drive, servo motor, industrial display screen, industrial keyboard, controller, encoder, regulator, sensor, I/O board, counting board, optical fiber interface board, acquisition card, gas turbine card, FIM card and other automatic spare parts
ABB — AC 800M controller, Bailey, PM866 controller, IGCT silicon controlled 5SHY 3BHB01 3BHE00 3HNA00 DSQC series
BENTLY — 3500 system/proximitor, front and rear card, sensor, probe, cable 3500/20 3500/61 3500/05-01-02-00-001 3500/40M 176449-01 3500/22M 138607-01
Emerson — modbus card, power panel, controller, power supply, base, power module, switch 1C31,5X00, CE400, A6500-UM, SE3008,1B300,1X00,
EPRO — PR6423 PR6424 PR6425 PR6426 PR9376 PR9268 Data acquisition module, probe, speed sensor, vibration sensor
FOXBORO — FCP270 FCP280 FCM10EF FBM207 P0914TD CP40B FBI10E FBM02 FBM202 FBM207B P0400HE Thermal resistance input/output module, power module, communication module, cable, controller, switch
GE —- IS200/215/220/230/420 DS200/215 IC693/695/697/698 VMICPCI VMIVME 369-HI-R-M-0-0-E 469 module, air switch, I/O module, display, CPU module, power module, converter, CPU board, Ethernet module, integrated protection device, power module, gas turbine card
HIMA — F3 AIO 8/4 01 F3231 F8627X Z7116 F8621A 984862160 F3236 F6217 F7553 DI module, processor module, AI card, pulse encoder
Honeywell — Secure digital output card, program module, analog input card, CPU module, FIM card
MOOG — D136-001-007 Servo valve, controller, module
NI — SCXI-1100 PCI – PXIE – PCIE – SBRIO – CFP-AO-210 USB-6525 Information Acquisition Card, PXI Module, Card
Westinghouse — RTD thermal resistance input module, AI/AO/DI/DO module, power module, control module, base module
Woodward — 9907-164 5466-258 8200-1300 9907-149 9907-838 EASYGEN-3500-5/P2 8440-2145 Regulator, module, controller, governor
YOKOGAWA – Servo module, control cabinet node unit
Main products:
PLC, DCS, CPU module, communication module, input/output module (AI/AO/DI/DO), power module, silicon controlled module, terminal module, PXI module, servo drive, servo motor, industrial display screen, industrial keyboard, controller, encoder, regulator, sensor, I/O board, counting board, optical fiber interface board, acquisition card, gas turbine card, FIM card and other automatic spare parts
