Programmable controller module identification by interconnecting the input and output ports of a module in a predefined manner

In a programmable controller having a processor for executing a control program which defines the operation of a machine to perform a specific function, a module with given functional characteristics for interfacing the processor to the machine, and address and data buses to which the processor and the module are electrically coupled;

• the module comprising:
• means coupled to the address and data buses for electrically interfacing with the processor;
• means for electrically interfacing with the machine in response to signals on the data bus;
• an output port which when enabled by a first signal on the address bus applies data from the data bus to a set of port output lines;
• an input port which when enabled by a second signal on the address bus applies data from a set of port input lines to the data bus;
• and
• means for coupling a first defined number of port output lines to a second defined number of port input lines in a pattern defined by functional characteristics of the module.

A module for a programmable controller in which the programmable controller has a processor coupled to an address bus and a data bus;

• said module comprising:
• means for electrically coupling said module to the address and the data buses;
• a first port means for applying data from the data bus to an output in response to a signal on the address bus;
• a second port means, having an input for receiving data, for applying data from the input to the data bus in response to a signal on the address bus;
• and
• means for coupling the output of said first port means to the input of said second port means in a manner that encodes data identifying characteristics of said module when data is read from said second port means by the processor.