Communication multiplexer variable priority scheme
AssigneeHoneywell Information Systems Inc.
InventorsAllen C. Hirtle, Gary J. Goss
Life of this patent
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Abstract
A communication multiplexer stores the receive and transmit channel numbers of input/output devices coupled to the multiplexer by communication lines in a first-in-first out (FIFO) memory. The input/output devices are polled by sending the channel numbers from the FIFO to the input/output devices. An input/output device requesting service responds to its channel number. The remaining channel numbers in the FIFO are recirculated to give the receive channel numbers priority over the transmit channel numbers. This gives high priority to a most recently used receive channel operative in a burst mode and equal priority to all transmit channels.
Claims8
A data processing system for transferring data bytes comprising:
- a system bus;
- a main memory coupled to said system bus for storing said data bytes;
- a communication multiplexer coupled to said system bus for transferring said data bytes between said main memory and a plurality of devices, each device being enabled for operation in a receive and a transmit mode respectively in response to receive and transmit channel numbers from said communication multiplexer;
- said communication multiplexer including polling means for sending a predetermined sequence of said receive channel numbers and said transmit channel numbers to said plurality of devices and receiving a request signal when one of said plurality of devices requests service by responding to said receive or transmit channel number;
- said polling means including:
- counter/register means for generating a first sequence of channel numbers during an initialization operation;
- first multiplexer means in a first state coupled to said counter/register means for receiving each of said first sequence of channel numbers;
- first in-first out (FIFO) means coupled for storing each of said first sequence of channel numbers;
- said FIFO means being coupled to said counter/register means for recirculating said first sequence of channel numbers during a polling operation, said plurality of devices being coupled to said counter/register means and responsive to said recirculating receive and transmit channel numbers for generating said request signal when one of said plurality of channel numbers requesting service receives a preassigned channel number of said first sequence of channel numbers.
Dependencies are inferred from the claim text.