Introduction

In a single transaction, the MSTR read and write operations can transfer data from a master source device to a specified slave destination device, then transfer data from this specified slave source to the master. It uses a master transaction path and may require several cycles to complete. To program an MBP_MSTR block to perform a combined read/write operation, use function code 23.

The combined read/write operation can be used only with these models:

  • Quantum: NOE 771 01 (3.0 or later) or NOE 771 11 (3.0 or later)

  • Momentum: M1E CPU (1.0 or later)

Control Block Usage

Register

Content

CONTROL[1]

23 = read/write data.

CONTROL[2]

Indicates the error status.

CONTROL[3]

Number of registers to be sent to the slave.

CONTROL[4]

Specifies the %MW starting register in the slave to which the data will be written, e.g. 1 = %MW1, 49 = %MW49.

CONTROL[5]

Routing register:

Most significant byte: network adapter module slot.

Least significant byte: MBP on Ethernet Transporter (MET) mapping index.

CONTROL[6]

...

CONTROL[9]

Each address contains 1 byte of the 32-bit IP address, where the MSB is in CONTROL[6] and the LSB is in CONTROL[9].

CONTROL[10]

Number of registers to be read from slave.

CONTROL[11]

Specifies the %MW starting register in the slave from which the data is read, e.g. 1 = %MW1, 49 = %MW49.
NOTE: When configuring the MBP_MSTR block for a read/write data operation, note that

  • The DATABUF output parameter is used to store, in the following sequence, both:

    1

    the data to be written
    2

    the data to be read

  • The size of the DATABUF output parameter must equal the combined size of the data to be written and the data to be read; if the size is smaller, data will be overwritten and may be lost.

  • Both the CONTROL and DATABUF parameters must be stored at located addresses, for example %MW addresses.