What is an MSP Driver?
The user can copy the driver into their program by opening the driver
file. The desired rungs can be highlighted and copied from the driver program. Next the
user will open the target program, position the cursor where desired and paste into the
target program. Alternately the user could start with our driver and paste their rungs
into it or build their program from it.
Drivers.
DRIVER |
DL105 |
DL205 |
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 |
Output Drivers.
Different Models.
a) PLC Direct's programming language and memory layouts is similar in all
models.
b) In general, language and memory in the lower model numbers are subsets
of the higher model numbers. The DL105 represents a reasonable lowest common denominator.
Single channel drivers and the driver subroutines are written to work in the DL105 and
should work with very little revision in all models.
c) The exceptions to item "b" are the DL330 and DL340 CPUs.
These represent the oldest models in the product line. They lack many instructions and
features. It would be difficult to convert the driver to fully function in the models. A
reduced version of the driver without delta calculations would be possible. In a DL305
system we recommend using only the DL350 CPU
d) Models with relay outputs can be used but care must be taken to
conserve relay life. See the sections on outputs regarding these modules.
Multiplexed Drivers.
Memory Usage.
Timing Parameters.
| Input |
|
| Protocol |
Delta |
| Scan Time |
10 msec (See Note 11) |
| 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 |
10 msec (See Note 11) |
| 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.
Scan Time.
The DL105 and DL205 execute the driver code in a time interrupt. The time
interrupt uses the High-Speed Interrupt mode (Mode 40) of the HSIO circuit. Execution of
the interrupt is set up in the first line of logic in the main program. The high-speed
interrupt mode is selected by setting in the lower of V7633 to the mode number 40 (BCD).
The scan time of the timed interrupt is in the upper 3 digits of the BCD value in V7634.
These three digits are in msec. The least significant digit must be equal to 4. Example
for 10 msec scan enter 104, for 15 msec scan enter 154. Interrupt processing must be
enabled with the ENI instruction. The driver program begins at the INT 0 instruction.
Inputs are updated in the beginning of the time interrupt subroutine and outputs are set
at the end by using immediate I/O instructions.
Software input filters are set in V7635 for X0 and X1, V7636 for X2 and
V7637 for X3. The filter time in msec is contained in the first two digits of the BCD
value in these registers. The last two digits of the BCD value in the register are always
"06". If these inputs are used for the MSP there filter time should be set for
the minimum, "00". Therefore the registers for input filters used by the MSP
should be set to 0006 (BCD). Inputs X4 and above have only hardware filters that are built
into the input modules.
See the user manual on the DL105 for more information on how the HSIO
circuit functions and the time interrupt works. From testing we have found that the DL205
time interrupt works identical to the DL105. PLC Direct support confirms that Mode 40 of
the HSIO in the DL205 works the same whether or not the counter interface module is
present. Do not use the manual on the DL205 for information about the time interrupt. Much
of the information in the DL205 manuals dated 6/97 and earlier is incorrect and
misleading.
On the DL105 best results can be obtained by using inputs X0 to X3. These
inputs are higher speed than X4 and above. Higher numbered inputs are usable just not
preferred. On the DL205 the inputs on the counter interface module are the fastest and are
preferred. The DL205's DC input modules have much longer filters and testing has shown
them to work acceptably. In extreme cases if unstable operation is observed it may be
necessary to slow the interrupt scan rate down for these modules.
Scan Time Exceptions.
On some older models it may have to be slowed down more. 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 50 msec.
Programming Results.
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.
DV-1000 Data Access Unit.
High Speed Counter (HSC).
The HSC driver uses the single channel High-Speed Counter mode of the
HSIO. In the DL105 family only one (1) channel is possible. See manuals for additional
information on the HSIO.
In all other families a special modules is required for the high-speed
counter. For the DL305 and DL405 families the cost would probably make this approach
uneconomical. In the DL205 family the high-speed counter module is fairly inexpensive. On
the DL240 and DL250 two (2) channels are possible.
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.
Beware of unstable operation at low frequencies and high scan rates. With
only the driver program in the DL105 the scan time was so fast that HSC was not updated
every scan when the frequency was less than 5 kHz. When the user adds their program and
the minimum scan time exceeds 2 msec. the frequency can be reduced if required
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 fourth 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 |
