How to install GE Series 90-70 Genius Bus Controller?

Maximum number of devices: 32 devices at 153.6 Kbaud standard, 153.6 Kbaud extension, or 76.8 Kbaud; At 38.4 Kbaud, there are 16 devices, including a bus controller, and usually one handheld monitor.

Data encoding: Each bit is encoded as three double pulses, and the receiver performs a majority vote to correct any single double pulse error. Double pulse is an AC code consisting of a positive voltage followed by a negative voltage offset, which is sampled separately to suppress low-frequency and high-frequency interference.

Modulation technique: Frequency Shift Keying (FSK) 0 to 460.8 KHz maximum (153.6 Kilobaud).

Isolation: 2000V high voltage, 1500V transient common mode suppression.

Signal to noise ratio: 60 dB.

Bus controller operation

The bus controller handles all data transfers between the PLC and devices on the bus, requiring the docking of two completely independent and asynchronous activities: Genius bus scanning (the communication cycle between devices on the bus, following the order of bus addresses 0-31) and CPU scanning (including the operation cycle of communication between the CPU and the bus controller).

The bus controller manages data transfer between the bus and CPU by maintaining two independent onboard RAM memories, one with the bus interface and the other with the CPU interface. The bus controller automatically transfers data between these two memories and provides data to the bus or CPU when needed.

Genius bus scan: Bus scan includes a complete cycle of "tokens" between devices on the bus, which may include other bus controllers or remote I/O scanners, as well as Genius modules. During bus scanning, the bus controller automatically performs operations such as receiving all input data sent by devices on the bus, broadcasting global data, updating outputs (if allowed), receiving any fault messages sent by devices on the bus and setting diagnostic status references for CPU use, and sending individual commands received from the CPU to the corresponding devices. The time required for communication tokens to be transmitted to all devices depends on the baud rate, the number and type of devices on the bus, and the usage of global data and datagram communication.

Input data from devices on the bus: Every time a module or remote I/O scanner has a communication token, the bus controller receives the input data they send (as this data is broadcast, it may be received by any other bus interface module running on the bus). The bus controller stores all received input data, and the CPU reads all discrete and analog inputs from the bus controller every time it scans (analog data is not multiplexed).

Output data from CPU: As the application program executes, the CPU sends output and any commands to the bus controller, which stores this data and transmits it on the bus every time it has a communication token. Unlike the input of broadcasting, the output is directed to the specific device that should receive them.

Diagnosis: Genius modules and other devices on the bus will automatically report faults, alarms, and certain other predefined conditions to the PLC. During any bus scan, only one diagnostic message can be sent. If a fault message has already been sent (by another device) during that scan, the device will save its diagnostic message to the next available bus scan. The bus controller stores any diagnostic messages received, and the Series 90-70 CPU automatically reads them. The Logicmaster 90-70 software can then be used to display the fault in the fault table and clear it from the programmer. For details, see Chapter 4. Genius handheld monitors can also be used for diagnosis and troubleshooting. In addition to the built-in diagnostic capabilities of Genius devices, the Logicmaster 90-70 application can also utilize other diagnostic mechanisms provided by the Series 90-70 PLC, such as system state references defined for Genius, fault and fault free contacts that can be used to detect faults and no fault conditions, and alarm contacts that can be used to indicate when simulated values reach specified alarm limits.

Datagrams

The Series 90-70 bus controller supports all Genius datagrams, including Read ID、Read ID Reply、Read Configuration、Read Configuration Reply、Write Configuration、Assign Monitor、Read Diagnostics、Read Diagnostics Reply、Write Point、Read Block I/O、Read Block I/O Reply、Report Fault、Pulse Test、Pulse Test Complete、Clear Circuit Fault、Clear All Circuit Faults、Switch BSM、Read Device、Read Device Reply、Write Device、Read Data、Read Data Reply、Write Data、Read Map、Read Map Reply、Write Map  Wait, each type of datagram has its specific description and function.

Global Data

Global data is automatically and repeatedly broadcasted by the bus controller. The Series 90-70 bus controller can send up to 128 bytes of global data per bus scan and receive up to 128 bytes of global data from each bus controller on the bus per bus scan.

Sending global data: Once configured (see Chapter 3), global data will be automatically broadcasted. Other bus controllers that receive global data sent by Series 90-70 PLCs will place it in different memory locations. For example, Series 90-70 PLCs will place it in the corresponding memory according to the configuration of the receiving bus controller, and Series 90-30 PLCs will place it in the% G memory location corresponding to the device number (16-23) of the Series 90-70 bus controller that sends data.