Материал: m013800e
5.1.1.1 Standard settings
The coupler is supplied with the following standard settings:
Designation |
Setting |
FR |
FR |
FR |
FR |
FR |
FR |
P1 |
P2 |
P3 |
P4 |
P5 |
P6 |
P7 |
P8 |
Chapt. |
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1 |
2 |
3 |
4 |
5 |
6 |
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Baud rate |
9600 Bd |
off |
on |
on |
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5.1.1.2 |
Byte Frame |
No Parity, 8 Bit |
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off |
off |
off |
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5.1.1.3 |
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1 Stop Bit |
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End of Frame |
3 x Frame Time |
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off |
off |
off |
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5.1.1.4 |
Time |
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Mode |
RTU mode |
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on |
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5.1.1.5 |
Error Check |
to be processed |
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on |
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5.1.1.6 |
Extended |
without |
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off |
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5.1.1.7 |
Functions |
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Watchdog |
switched on |
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off |
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5.1.1.8 |
Update |
normal |
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off |
5.1.1.9 |
Firmware |
operation |
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Table 5.1: Standard settings, coupler
5.1.1.2 Baud rate setting
The baud rate is set using DIP switches FR 1 to FR 3.
Baud rate |
Baud rate |
FR1 |
FR2 |
FR3 |
750-312/314 |
750-315/316 |
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150 Bd |
38400 Bd |
off |
off |
off |
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300 Bd |
57600 Bd |
on |
off |
off |
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600 Bd |
115200 Bd |
off |
on |
off |
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1200 Bd |
1200 Bd |
on |
on |
off |
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2400 Bd |
2400 Bd |
off |
off |
on |
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4800 Bd |
4800 Bd |
on |
off |
on |
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9600 Bd |
9600 Bd |
off |
on |
on |
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19200 Bd |
19200 Bd |
on |
on |
on |
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Table 5.2: Baud rates, coupler
The standard setting is 9600 Baud.
26 |
MODBUS / Configuration |
15.12.99
5.1.1.3 Error detection, length of the character string
A parity bit can additionally be transmitted with each byte. Data transfer faults are detected with the help of the parity bit. A differentiation is made between parity checks for even parity, odd parity and no parity.
For this the number of set bits (=1) are counted in the transmitted data bytes. For example, with the transmission of the character string 1100 0101 the number of set bits is even, namely 4. If the setting of an even parity bit is selected, then in this case it is set to 0, so that the number of set bits still remains even. Analog to this, the odd parity bit 1 would be selected so that the number of set bits will be odd.
This type of error detection is assured with one error, with several errors under certain circumstances this may no longer be assured. If the coupler recognises a parity error, the frame is ignored and a new frame can only be received following a renewed ‘Start of Frame’.
If the slave receives faulty frames, this will not be replied to. The master detects this error in that after the preset time (Time-out) no corresponding frame was received.
In the MODBUS coupler 750-312 a parity bit can be attached to each byte. The data length can be selected for 7 or 8 bit. In addition it is possible to add 1 to 3 stop bits.
Byte Frame |
Data length |
Stop Bits |
FR4 |
FR5 |
FR6 |
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No Parity |
8 |
1 |
off |
off |
off |
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Even Parity |
8 |
1 |
on |
off |
off |
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Odd Parity |
8 |
1 |
off |
on |
off |
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No Parity |
8 |
2 |
on |
on |
off |
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No Parity |
7 |
2 |
off |
off |
on |
Even Parity |
7 |
1 |
on |
off |
on |
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Odd Parity |
7 |
1 |
off |
on |
on |
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No Parity |
7 |
3 |
on |
on |
on |
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Table 5.3: Byte Frame, coupler
The standard setting is no parity, 8 bit data length and 1 stop bit.
During transmission in RTU mode the DIP switch FR6 is ignored, as the format is set to 8 bit in this mode.
MODBUS / Configuration |
27 |
15.12.99
5.1.1.4 End of Frame Time
The end of frame time is the pause time following a frame, which is required to switch over the repeater in slave. This time must permit gaps during a frame which will not result in a faulty recognition of the end of frame time. The setting of the end of frame time is made with DIP switches P1 to P3.
End of Frame Time |
P1 |
P2 |
P3 |
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3 x Frame Time |
off |
off |
off |
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100 ms |
on |
off |
off |
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200 ms |
off |
on |
off |
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500 ms |
on |
on |
off |
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1 s |
off |
off |
on |
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1 ms |
on |
off |
on |
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10 ms |
off |
on |
on |
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50 ms |
on |
on |
on |
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Table 5.4: End of Frame Time, coupler
The standard setting is 3 x frame time. The settings 1 ms, 10 ms and 50 ms are only implemented as from firmware version 2.5 of the MODBUS coupler.
5.1.1.5 ASCII/RTU mode
MODBUS permits two different transmission modes:
ASCII mode: |
Each byte (8 Bit) is sent as a 2 ASCII characters. |
Advantages: |
Displayable characters are transmitted. The gaps between characters |
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need not be observed, provided they do not exceed 1 second. |
RTU mode: |
Each byte (8 Bit) comprises of two 4 bit hexadecimal characters. |
Advantages: |
As only 1 character has to be transmitted for each byte a higher data |
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throughput is achieved in comparison to the ASCII mode. |
The setting is made using DIP switch P4.
Mode |
P4 |
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ASCII |
off |
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RTU |
on |
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Table 5.5: ASCII-/RTU mode, coupler
The standard setting is RTU mode.
28 |
MODBUS / Configuration |
15.12.99
5.1.1.6 Error Check
A check sum (CRC) is calculated from the frame to be transmitted in the sender (higher ranking controls). This check sum is transmitted in the frame to the receiver (coupler). Once the error check is activated, this check sum is compared with the check sum calculated in the coupler on the basis of the same instruction. An error is signalled by a red LED ‘CRC’.
ATTENTION:
Do not set this option during operation!
The error check is set with the DIP switch P5.
Error Check |
P5 |
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ignored |
off |
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being processed |
on |
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Table 5.6: Error Check, coupler
The standard setting is the switched on error check.
5.1.1.7 Extended Functions
The register for further internal diagnostic possibilities (extended functions) in the address space of the coupler are not yet available. For this reason do not change the DIP switch P6 standard setting (off).
Extended Functions |
P6 |
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without |
off |
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available |
on |
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Table 5.7: Extended Functions, coupler
In the standard setting, other diagnostic possibilities are switched off.
MODBUS / Configuration |
29 |
15.12.99
5.1.1.8 Watchdog
The watchdog serves for monitoring the data transfer between the higher ranking controls and the coupler. If no communication has occurred after a default time, the node is set into a secured status, i.e. the digital outputs of the node are set to 0 and the analog outputs are set to the minimum value (e.g. with 4...20 mA to 4 mA).
The watchdog is switched on with DIP switch P7.
Watchdog |
P7 |
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switched on |
off |
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switched off |
on |
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Table 5.8: Watchdog, coupler
The standard setting is with the watchdog switched on.
Selection of the watchdog is described in more detail in chapter 5.3.2.
5.1.1.9 Update Firmware
The DIP switch P8 releases the loading of a new firmware. This function has not yet been implemented, for this reason do not change the standard setting (off) of the switch.
ATTENTION:
Only switch over the DIP switch P8 to update the firmware. Switching over during operation may lead to a malfunction!
Update Firmware |
P8 |
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normal operation |
off |
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Update Firmware |
on |
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Table 5.9: Update firmware, coupler
The standard setting is normal operation.
30 |
MODBUS / Configuration |
15.12.99