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 method and apparatus for transferring data between two data processors includes transferring a data byte from the first processor to a latch member, setting a flip-flop circuit which generates an interrupt signal to the second processor enabling the second processor to transfer the data byte from the latch member to a RAM memory unit associated with the second processor. The second processor resets the flip-flop circuit which outputs a signal to the first processor enabling the first processor to transfer another data byte to the latch member. Steering address bits associated with each of the processors are used to provide control signals to select the storage member in which the data bytes are to be transferred. A second flip-flop circuit associated with the second processor allows the second processor to transfer data to the first processor in the same manner.