You have a ControlLogix PLC and someone just added a Modbus TCP flow meter to your project. Studio 5000 opens, you look for the “Modbus TCP” option in the module tree… and it is not there. Not in the standard modules. Not in the add-on profiles. Not in the Ethernet configuration. That is because ControlLogix has no native… Read More »
Modbus and MQTT solve the same problem from opposite ends. Modbus reads and writes numbers in a device. MQTT moves messages between systems. Put them together and you can take a register sitting inside a serial meter and land its value in a cloud database a continent away. But the two don’t connect on their own — they… Read More »
MQTT is deliberately unopinionated about what your payloads contain, how you structure your topics, or how devices announce themselves to the network. That flexibility is a big part of why MQTT is popular. It is also the reason MQTT alone is not enough for industrial IoT, where two vendors’ devices need to interoperate on the same broker, where… Read More »
If you write Python and you need to move small messages between devices or services, MQTT is usually the right fit. It is a publish/subscribe protocol: a client sends a message to a topic, a broker holds the connections, and every client subscribed to that topic gets a copy. Publishers and subscribers never talk to each other directly.… Read More »
XON and XOFF are two control characters that let a serial receiver tell a sender to pause and resume. That’s the whole idea behind software flow control. No handshake wires, no dedicated signals — just two bytes sent back up the same link the data travels on. When a device can’t keep up, it sends XOFF and the… Read More »
A null modem cable connects two DTE devices directly — two PCs, a PC and a controller console port, two pieces of test gear — with no modem in between. The whole job lives in the wiring. Transmit on one end has to reach receive on the other, and depending on the device, a few control lines have… Read More »
On a Modbus serial line, every byte you send is wrapped in a few extra bits before it hits the wire. Those extra bits — the start bit, an optional parity bit, and one or two stop bits — make up the character format. Get them wrong on one device and it won’t talk to the rest of… Read More »
Device control is where ICCP stops being a data feed and becomes an operational tool — and a liability if misunderstood. Conformance block 5 lets one control center trip breakers, raise taps, and write setpoints in another organization’s network. The protocol wraps that power in the select-before-operate pattern every operations engineer knows from local SCADA, adapted for the… Read More »
An ICCP link is a standing, months-long connection between two organizations, carrying real-time grid data and — where block 5 is enabled — live control of primary equipment. It crosses an organizational boundary by definition: the other end is somebody else’s network, somebody else’s patching discipline, somebody else’s incident. That makes it one of the most security-relevant connections… Read More »
A transfer set is the engine of an ICCP link. Data values are what you exchange; data sets group them; but the transfer set decides everything about the actual flow — when reports are sent, what they contain, how bursts are handled, and whether the client must acknowledge. Once transfer sets are enabled, the link runs itself: the… Read More »