GE EPM 9650/9800 Sequence for Port Locking, Transmission, Reception, Port Unlocking Sequence

5.2.1: Sequence for Port Locking

To lock a port, follow the steps below:

1.Determine the port to which the Modbus Master is currently attached: Register 65411.

2.Determine that the desired port is currently unlocked: Registers 41730 – 41732.

3.Write to lock the desired port: write 0100H – 0104H to Register 41729.

4.Verify that the port is successfully locked: Registers 41730 – 41732.

5.Read the current states of the pointers: 41733 – 41752.

5.2.2: Transmission

1.Decide which transmit buffer to use: Registers 43265, 43521, 43777, 44033, 44289.

2.Find the current position of the TrmIn pointer: Registers 41735, 41739, 41743, 41747, 41751.

3.Add bytes to the transmit buffer starting at the position indexed by the TrmIn pointer up to the position before that indexed by the TrmOut pointer.

4.Write the new value for the TrmIn pointer (the position after the last byte added) to the TrmIn pointer.

5.2.3: Reception

1.Decide which receive buffer to use: 41985, 42241, 42497, 42753, 43009.

2.Find the current position of the RecOut pointer: 41734, 41738, 41742, 41746, 41750.

3.Read bytes starting at the position after that indexed by the RecOut pointer, up to the position before the position indexed by the RecIn pointer.

4.Write the new value for the RecOut pointer (the position of the last byte read) to the RecOut pointer.

5.2.4: Port Unlocking Sequence

To unlock a port, follow the steps below:

1.Empty the receive buffer (RecOut written so it is the position before RecIn).

2.Write to unlock the desired port: write 0200H – 0204H to Register 41729.

3.Verify that the port is successfully unlocked: Registers 41730 – 41732.

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