Abstract:
A data communications subchannel includes apparatus for separately testing the operation of the send control logic and the receive control logic. During testing operations the subchannel is configured in a wraparound mode so that data sent from a processor is routed through the send control logic and the receive control logic back to the processor. A ''''Cyclic Redundancy Check'''' is performed on the return data to determine if any errors are present. If errors are present in the return data the send control logic and the receive control logic can be selectively bypassed to aid in determining where the errors originate. Special control signals from the processor are used to configure the subchannel into the modes which perform the error testing.
Abstract:
A data communications subchannel uses input signals and decoding logic to select the baud rate, the length of message characters, the mode of operation and the number of stop bits in a message character used in transmitting binary message characters between a data communications subchannel and a terminal device.
Abstract:
Apparatus for maintaining character synchronization in a data communication system comprises a buffer to store characters being transferred from a communications controller to a terminal device, a shift register connected between the buffer and the terminal device and a source of fill characters which provides characters to fill any gap between message characters provided by the communications controller.