Extensibility > Using an OPC DA Server > OPC DA Server Reference Information > OPC Client Read Request Conversions

OPC Client Read Request Conversions

The following table describes the outcomes that can be expected when converting Citect SCADA data types to OPC data types during client read requests.

OPC Data Types
(To)

Citect SCADA Data Types (From)

BYTE

INT

UINT,
BCD

LONG

ULONG,
LONG-
BCD

REAL

STRING
(256 bytes)

DIGITAL

I1

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

OK

UI1

OK

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

OK

I2

OK

OK

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

OK

UI2

OK

Overflow
if out of
range

OK

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

OK

I4

OK

OK

OK

OK

Overflow
if out of
range

Overflow
if out of
range

Overflow
if out of
range

OK

UI4

OK

Overflow
if out of
range

OK

Overflow
if out of
range

OK

Overflow
if out of
range

Overflow
if out of
range

OK

R4

OK

OK

OK

OK

OK

OK

Overflow
if out of
range

OK

R8

OK

OK

OK

OK

OK

OK

Overflow
if out of
range

OK

CY

OK

OK

OK

OK

OK

OK

Overflow
if out of
range

OK

DATE

OK

OK

OK

OK

OK

OK

Overflow
if out of
range

OK

BSTR

OK

OK

OK

OK

OK

OK

OK

OK

BOOL

OK

OK

OK

OK

OK

OK

Overflow
if out of
range

OK

Note: For read operations that result in an overflow, OPC E_FAIL will be returned and read quality will be set to BAD.

See Also

OPC client write request conversions
OPC DA Server reference information

Published June 2018