Communications between central unit and peripheral units

Claim 2

In a system including a control unit coupled to a plurality of peripheral devices, in combination: means at each peripheral device for producing a flag signal to indicate that it needs servicing; means at the control unit for transmitting to all peripheral devices, during a period none of them is being serviced, an interrogate signal for placing in a first queue the ones of the peripheral devices producing a flag signal; means at the control unit for then servicing, in sequence, only the devices in the queue; means at each peripheral device for indicating when its servicing is completed; and means at the control unit responsive to an indication that the servicing of all peripheral devices in the first queue is completed, for placing in a new queue all devices at that time producing a flag signal.

Claim 3

In a system as set forth in claim 1, said means for servicing including means for transmitting to the first device in the queue a second interrogate pulse to indicate the start of a servicing period for that device.

Claim 4

In a system as set forth in claim 2, said control unit including means for transmitting interrogate signals sequentially at a rate such that many may occur during a period a peripheral device is being serviced; and each peripheral device including means for preventing an interrogate pulse it receives during a period it is being serviced from being transmitted to the next device in the queue.

Claim 5

In a system for communicating between a central control unit and a plurality of peripheral devices, at each peripheral device: a. first and second flip-flops normally in their reset state; b. means responsive to an interrogating pulse when the first flip-flop is in its reset state for applying that pulse to means at the following peripheral device; c. means responsive to an interrogating pulse, a locally produced flag signal and a signal indicating that none of the peripheral devices is being serviced, for setting said first flip-flop and preventing subsequently occurring interrogate pulses from being applied to means at the following peripheral device; d. means responsive to the interrogating pulse following the one which sets the first flip-flop for setting said second flip-flop; e. means responsive to the termination of said flag signal followed by an interrogate pulse for resetting said first flip-flop; f. means responsive to the reset first flip-flop and the set second flip-flop for producing an end-of-operation signal; and g. means responsive to the interrogate pulse following the one which resets the first flip-flop for resetting the second flip-flop.

Claim 6

In a system for communicating between a central control unit and a plurality of peripheral devices, at each peripheral device: a. first and second flip-flops normally in their reset state; b. means responsive to an interrogating pulse when the first flip-flop is in its reset state for applying that pulse to means at the following peripheral device; c. means responsive to an interrogating pulse, a locally produced flag signal and a signal indicating that none of the peripheral devices is being serviced, for setting said first flip-flop and preventing subsequently occurring interrogate pulses from being applied to means at the following peripheral device; d. means responsive to the interrogating pulse following the one which sets the first flip-flop for setting said second flip-flop; e. means responsive to the termination of said flag signal followed by an interrogate pulse for resetting said first flip-flop; f. means responsive to the reset first flip-flop and the set second flip-flop for producing an end-of-operation signal; and g. means responsive to the interrogate pulse following the one which resets the first flip-flop for resetting the second flip-flop.

Claim 7

In a system as set forth in claim 4, further including: means at each peripheral device for producing an end-of-operation signal when that device is the last one in a group of devices whose servicing has been completed.

Claim 8

In a system as set forth in claim 5, further including: Means at each peripheral device for maintaining said first flip-flop in its set state, once it has been set, for as long as said flag signal is present and for maintaining said first flip-flop in its reset state, once it has been reset, for as long as said end-of-operation signal is absent.