Abstract: A method of measuring message response time performance of a data processing system includes the generation of timing messages when a data or status message is sent from a data terminal, such as a point of sale terminal in the system to a central processing unit, and when a data message is received at the terminal from the central processing unit. The timing messages include identification of type of message, time data taken from a timer in the terminal, and a sequence number which permits related messages to be paired so that the time values in each can be compared to determine a response time for the total period required for transmission of messages from the terminal to the central processing unit, any necessary data processing at the central processing unit and transmission of a message from the central processing unit back to the terminal.

Abstract: A data processing system which includes a host processor and a plurality of remote processing devices which are coupled to a common communication channel. The system also includes a look-up table storing the sets of instructions for a plurality of communication protocols for use with the remote processing device and a controller associated with one of the remote processing devices. A selectively actuated switch member located in the controller provides an address for the controller. During a power-up operation, the controller address is transmitted to the host processor for use in addressing the look-up table to obtain the communication protocol for the controller. This information is then loaded into the controller for controlling the transfer of data between the host processor and the remote processing device.

Abstract: A method for polling a plurality of remote processing units includes establishing a table of active and inactive remote processing units, sequentially polling each of the active processing units, at the conclusion of polling the active processing units, polling an inactive processing unit after which all of the active processing units are again polled. This sequence is repeated until all the active and inactive processing units have been polled. If in polling a processing unit, a response to the poll message indicates a change of status of the polled processing unit has occurred, the table is accordingly updated to reflect the current status of the processing unit.