DF1 OPC Items

Append a '/' to the register or status items followed by a bit number (starting at zero (0)) to access a single bit of a multi-bit data type.

For example, N7:3/3 would access the third bit of N7:3.

A bit-width can be specified by appending a '.' followed by a number after the bit number specifier ('/').

For example, N7:3/3.2 would access the third and fourth bits of N7:3 and return them as an integer.

Append an ‘!’ to a Boolean to invert the value.

For example, N7:3/3! would access the third bit of N7:3 and invert the value.

Append an 'I' to the register to access the data as a single, unsigned 16-bit integer value.

For example, N7:3I would access the first 2 bytes at N7:3 and return it as an unsigned 16-bit integer - even if the register is native 32-bit.

Append an ‘IS’ to the register to access the data as a single, signed 16-bit integer value.

For example, N7:3I would access the first 2 bytes at N7:3 and return it as a signed 16-bit integer - even if the register is native 32-bit.

Append an ‘L’ to the register to access the data as a single unsigned, 32-bit integer value.

For example, N7:3L would access the first 4 bytes beginning at N7:3 and return it as an unsigned 32-bit integer. If the register is native 16-bit, ACM will request both N7:3 & N7:4 and combine the result into a single value.

Append an ‘LS’ to the register to access the data as a single signed, 32-bit integer value.

For example, N7:3L would access the first 4 bytes beginning at N7:3 and return it as a signed 32-bit integer. If the register is native 16-bit, it will return N7:3 & N7:4 as a single value.

Append an ‘F’ to the register to access the data as a single 32-bit floating point value.

For example, N7:3F would access 4 bytes beginning at N7:3 and return it as a 32-bit floating point value. If the register is native 16-bit, it will return N7:3 & N7:4 as a single value.

Append a number in parentheses to override the native data type length in bytes. This was done for newer series PLCs that can be configured to emulate older device types and support the DF1 protocol.

For example, N7:2(4) tells ACM that N7:2 is a native 4 byte (32-bit) register. ACM will request one register and expect 4 data bytes.

Append a '^' and a byte order code number to the register to apply a specific byte order to the incoming and outgoing values.

For example, N7:10F^3 reads the 4 bytes starting at N7:10, changes the word order, and interprets the result as a floating point value. If the registers are native 16-bit, it will use N7:10 & N7:11 as a single value. See the byte order code numbers table below.