As previously stated, the GDEV block is very versatile and useful. We use GDEV blocks at every opportunity for all of the reasons mentioned in earlier posts. However, I remember a glaring weakness in an otherwise ideal block. Unlike a hardwired motor (or ladder logic), the GDEV will not remove the power request to the motor if the motor loses its feedback (auxiliary contacts). =20 I have worked around this by tying the MMAIND (Mismatch Alarm Indicator) into the INTLCK parameter, thus forcing the GDEV into its Interlock mode (and over-riding either Manual or Auto modes) to drive the GDEV off. I tie the INTDSR (Interlock Desired State) back onto itself (so that its state cannot be changed) and give it the default value of OFF. Once the GDEV output is OFF, the desired state matches the feedback state so the GDEV is no longer in Mismatch Alarm and the GDEV passes out of the Interlock mode and back into the Manual mode in the OFF state. The additional connections are as follows: INTLCK =3D :Blockname.MMAIND INTDSR =3D :Blockname.INTDSR.0 This solution assumes a few things, such as the assumption that the INTLCK parameter was otherwise not going to be used. The same assumption is made for the desired state of the Interlock, INTDSR. The most difficult consequence for us to live with is that the GDEV is left in the Manual mode. Most of the time, it has not been a problem. As always, "your mileage may vary". I am going from memory here, so will wish to verify my statements, test the results for yourself, etc. Chuck Jones Automation Technologist Tate & Lyle -- Lafayette Plant Office 765.477.5324 | Cell 765.586.5290 ***************************************************************************= ************************** This email and any files transmitted with it are confidential and intended = solely for the=20 use of the individual or entity to whom they are addressed. If you are not = the intended=20 recipient or the person responsible for delivering the email to the intende= d recipient, be=20 advised that you have received this email in error that any use, disseminat= ion,=20 forwarding, printing, or copying of this email is strictly prohibited. If = you have received=20 this email in error please notify the sender immediately. Please note that = we reserve=20 the right to monitor and read any emails sent and received by the Company i= n=20 accordance with and to the extent permitted by applicable legal rules. ***************************************************************************= ************************** _______________________________________________________________________ This mailing list is neither sponsored nor endorsed by Invensys Process Systems (formerly The Foxboro Company). Use the info you obtain here at your own risks. Read http://www.thecassandraproject.org/disclaimer.html foxboro mailing list: //www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave