ABTCP Driver Parameters

[ABTCP] Parameter

Allowable Values

Default Value

Description

Block

10 - 256

236

A value (bytes) used by the I/O Server to determine if two or more packets can be blocked into one data request before being sent to the I/O Device. For example, if you set the value to 10, and the I/O Server receives two simultaneous data requests - one for byte 3, and another for byte 8 - the two requests will be blocked into a single physical data request packet. This single request packet is then sent to the I/O Device, saving on bandwidth and processing.

Delay

0 to 300

0

The period (in milliseconds) to wait between receiving a response and sending the next command.

MaxBits

0 to 2048

1888

The maximum read size in one request. Decrease the value for non-standard I/O Devices that do not support large reads.

MaxBits should be a multiple of 8. If this value is modified from the default, then the protdir.dbf file in the Plant SCADA bin directory needs to be manually edited so that the MAX_LENGTH entry for your I/O Device is changed to match. For example, if MaxBits is set to 1920 bits for the ABTCP5 protocol then protdir.dbf should be modified as follows:

ABTCP5 AB5 944 1920 0x37f

MaxPending

1 -32

8

The maximum number of pending commands that the driver holds ready for immediate execution.

PollTime

0 to 300

0

The interrupt or polling service time (in milliseconds). Setting the polling time to 0 puts the driver in interrupt mode.

Note: If you are using the PKTX or the 5136-SDI-PCI board, this parameter should be set to 10.

Retry

0 - 8

1

The number of times to retry a command after a timeout.

Status

The value for this parameter is formatted as follows:

<RawType>, <BitWidth>, <UnitType>, <UnitAddress>, <UnitCount>

where...

RawType =
0 for Digital
1 for Int
4 for Long
8 for Byte

BitWidth =
1 for Digital
8 for Byte
16 for Int
32 for Long

UnitType =
Protocol specific. See the variable specification .DBF files for the particular PLC.

UnitAddress =
The item number or bit number.

UnitCount =
1 for Analog
16 for Digital

No default.

For example, to specify the time/date seconds counter S:23 as the status variable in a PLC-5/40E, use the following:

[ABTCP]
Status=1,16,0xd0002,23,1

Or, to use the processor status run mode bit S:1/1 for a PLC-5/10, use the following:

[ABTCP]
Status=0,1,0xd0002,17,16

Defines the register that indicates the status of the PLC (for Hot Standby). This register is checked every [ABTCP]WatchTime period.

Usually, if the PLC is put into program mode, communications continue as normal, so the operator is unable to tell that control is suspended. However, when this parameter is used, can be made to display #COM to signify that the PLC is offline (and the driver will return 0x20). If there is a standby unit configured, then it will automatically swap to it.

For this to work correctly, you may need to manually configure the status register in your PLC. The register needs to be configured as follows, depending on whether it is a digital or analog variable:

Digital - The variable needs to be always on, otherwise the unit is put offline.

Analog - The variable needs to be changed for each read. If the variable has not changed since the last read, the unit is put offline.

StringReverse

0 to 1

0

Set to 1 if the bytes in each word of a string needs to be swapped.

Timeout

0 to 32000

1000

Specifies how many milliseconds to wait for a response before displaying an error message.

WatchTime

0 to 128

30

The frequency (in seconds) that the driver uses to check the communications link to the I/O device.