Notes: GE Fanuc

Notes: GE Fanuc

90/Micro, 90/20, 90/30

Revision: 4.11

Download this page along with the Memory Usage and Wiring Diagrams as a Microsoft Word file "Notes.doc" for best printing. This file is included on the disks that come with the MSP and with all driver downloads.

What is an MSP Driver? An MSP driver is a small ladder logic program that is added to the user program. All code is standard ladder logic. In GE 90 Micro it requires set of lines of logic at the beginning of the main program. In modules supporting subroutines this logic could be divided into one to three subroutines. One line of logic in the main program calls the MSP Subroutine. This subroutine may be the complete driver or in some versions it may call one or two other subroutines.

The user can import the driver into their program by opening the driver file, selecting all the rungs, and writing them to a side file. Next the user will open their program position the cursor at the beginning of the ladder logic program and including the side file in their program. Alternately the user could start with our driver and build their program from it.

Drivers. The following is a list of drivers in the MSP Driver Library for the GE 90 MICRO PLC. These drivers were prepared with GE's LogicMaster Micro programming software, revision 3.01(31A1). The single channel input and single channel output drivers are available on the Driver Installation disks. All other drivers are available on our web site. They contain rung comments, address descriptions, and address symbols that are viewable in the programming package and on printouts.

DRIVER	DESCRIPTION
Msp_I	1 Channel Input
Msp_I_M	2 Channel Input Multiplexed
Msp_I_H	1 Channel Input, High Speed Counter
Msp_O	1 Channel Output
Msp_O_M	2 Channel Output Multiplexed
Msp_IO	1 Channel Input, 1 Channel Output
Msp_IO_M	2 Channel Input Multiplexed, 2 Channel Output Multiplexed

Different Models. All drivers for the 90 MICRO should work with very little revision on other

a) GE's programming language and memory layout are very similar in all models. In general, the 90 MICRO is a subset of the 90/30 and 90/70 series.

b) All models except the 90 Micro have subroutines, which would simplify the multiplexed drivers.

c) GE models. The 90/30 and 90/70 series are modular and solid state outputs are available. With solid state outputs speed can be increased without worry about relay life. The output modules are available in both sink and source versions. See the sections on inputs and output regarding these modules.

Timing Parameters. These drivers are set up for the Delta protocol. Following are some of the key timing parameters:

Input
Protocol	Delta
Scan Time	10 msec (See Note 9)
Full Word Bits	16 Bits
Delta Bits	4 Bits
Delta Refresh Count	16 Scan Refresh
ID Pulse Width	1.2 Scans
Data Pulse Width	3 Scans
Output
Protocol	Delta
Scan Time	50 msec (See Note 9)
Full Word Bits	16 Bits
Delta Bits	4 Bits
Delta Refresh Count	16 Scan Refresh
ID Pulse Width	3 Scans
Data Pulse Width	3 Scans

Quality Control File. Included with the files for each driver is a file of the same name with the ".sp" extension. This file contains the model and serial numbers of all hardware and software used for testing. This file also contains the setup parameters used for testing.

Scan Time. The key to getting the driver to function properly is to get the driver code executed and PLC I/O for the MSP updated at constant time intervals.

The 90 MICRO PLCs have the ability to fix the scan of the PLC. Constant scan time is set in the processor configuration package under "I/O Configuration". Use the arrow keys to move down to the field labeled "Sweep Mode". Use the tab key to change the field to "CNST SWP". Next use the arrow keys to move to the "Sweep Tmr" field and enter the desired time in msec.

The newer more powerful processors in the 90/30 series have periodic subroutines. If available the MSP driver should be run from this subroutine and the scan time could then float with the "Sweep Mode" set to "NORMAL". See the GE manuals for how to set this up. Note that inputs will have to be updated at the beginning the periodic subroutine using the DOIO instruction. Outputs will have to be set at the end by also using the DOIO instruction. See the GE manuals on how the DOIO instructions work.

Scan Time Exceptions. When possible the scan time is set at 10 msec. This is the default setting of the MSP. On some older models it may have to be slowed down. Those models with relay outputs must be slowed down when using MSP analog outputs. The mechanical relays are slow when compared to solid state and we us a scan time of 30 msec. Note that the Msp_IO_M driver effectively has 4 channels. For any of the multiplexed drivers that are expanded to 4 or more channels on any model the scan time should be watched closely and may have to be increased.

Programming Methods. One of the key programming methods is the use of memory locations that are accessed both as registers and bits. We used the M memory for this purpose. In several cases we use a shift register as a counters. A seed is planted in bit zero of the shift register word. To increment the counter by one the shift resistor is shifted one bit. This allows the current value of counter to be checked by testing a single bit in ladder, which is much more efficient than a whole register compare. These programs have been extremely optimized for both minimum scan time and memory usage.

Programming Results. Programming for GE processors yields excessively complex code. GE does not permit branching around block instructions, which is a serve limitation on making a program both understandable and efficient.

GE does support a continuation coil and contact. The mechanism intent is to all rungs longer than 10 columns but it can be used for another purpose. Though messy the mechanism can provide output branching for around block instructions. Once the continuation coil has been determined its status can be referenced multiple times by continuation contacts for different output branches. Once the status of the continuation coil is determined it is not changed until it is used again.

The ladder logic has been refined and optimized to a very high degree. In someways this may make the driver programs harder to read but it is felt that efficient use of memory and execution time are the most important factors.

High Speed Counter (HSC). The HSC driver is intended for the 90 Micro only. This driver uses less ladder logic memory but requires 2 inputs per channel. Depending on the value transmitted it may be faster or much slower than the Delta protocol. Unlike the Delta protocol the update time for the HSC protocol is not deterministic.

The HSC driver uses Type A counters and up to four (4) input channels are possible on a 90 Micro. The included driver is setup for a single channel on counter 1. The built in HSC is not available usable on the other modular 90/30 and 90/70 series. It would be possible using a similar approach with the high-speed counter module but the cost would be uneconomical. See the documentation on the HSC modules for specific details.

Much of the setup of the counter is in the configurator. The desired counters must be Type A. Each counter used must be enabled and the output disabled. The count mode must be continuos and the count direction must be up. The high count limit must be set to 32,767. The low count limit must be set to zero or some negative number. All of the other parameters are not used and can be set to any value. See manuals for additional information on the HSC.

The scan time on the MSP must be set greater than the maximum scan time of the PLC. We used 10 msec for test purposes even though the scan time of the PLC was less than 1 msec. This allows some room for the user to add their program. On the 90 Micro the scan time was fixed. With only the driver program in the 90 Micro the scan time was so fast that HSC was not updated every scan. The scan time was fixed just to slow down its rate of execution. If the user program has a minimum scan time of more than 2 msec. scan time could float.

In order to send a value of zero (0) or negative values an offset is added to the pulse count before transmission. The driver then subtracts this offset after counting the received pulses. Note the subtraction that occurs in the third rung. The value of the offset varies depending on the MSP model and scale factor in order to keep the offset to a minimum. The following table shows the offset for the different ranges. The constant in the second rung must be changed to match the configuration of the MSP.

MSP MODEL	SCALE FACTOR	OFFSET
MSP-RTD	X1	50
MSP-RTD	X10	500
MSP-TC	X1	50
MSP-TC	X10	500
All other models		1

As noted previously, each HSC uses two inputs. The MSP must be connected to the count input that is %I1, %I3, %I5, and %I7 for HSCs for channels 1, 2 3 and 4 respectively. The Preload/Strobe inputs are %I2, %I4, %I6, and %I8 for HSCs or channels 1, 2 3 and 4 respectively. If a counter is used for an MSP its corresponding Preload/Strobe input must remain disconnected and can not be used for other purposes.

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