Method and apparatus for serial data flow control

A method for controlling the flow of serial data from a data communications device to a host device when using a universal asynchronous receiver transmitter (UART) to convert said serial data from said data communications device to parallel data for said host device, said UART providing clock pulses at a predetermined frequency, having a buffer for the temporary storage of said parallel data, and providing a control signal when said buffer is empty, said method preventing the loss of said data, comprising the steps of:

• counting said clock pulses;
• providing a count signal responsive to the number of said clock pulses exceeding a predetermined value;
• clearing said count signal in response to provision of said control signal;
• and
• responding to provision of said count signal by instructing said data communications device to halt the transmission of said serial data.

In a system comprising a host device, a serial communications device containing a universal asynchronous receiver transmitter (UART), and a remote transmitter for sending the data to said host device by way of said serial communications device, said UART converting said data from a serial format into a parallel format, providing clock pulses at a predetermined rate, having a buffer for the temporary storage of said data and providing a first signal when said buffer is empty, an improvement to said serial communications device to prevent said buffer from overflowing by automatically signaling said remote to stop transmission of said data, comprising:

• first means for setting a pulse count to a first predetermined value in response to said first signal, for counting said clock pulses, and providing a second signal when said pulse count reaches a second predetermined value;
• second means responsive to provision of said second signal for rendering said first means non-responsive to said clock pulses;
• and
• third means responsive to provision of said second signal for providing a control signal to said remote transmitter to signal said remote transmitter to stop said transmission of said data.

An apparatus for controlling the flow of serial data from a data communications device to a host device, said apparatus preventing the loss of said data, comprising:

• a universal synchronous-asynchronous receiver transmitter (USART) comprising:
• receiver means for receiving said serial data from said data communications device, means for converting said serial data to parallel data, storage means for storing said parallel data, means for providing said parallel data to said host device, control means responsive to said storage means being empty for providing a control signal, and clock means for providing a clock signal having pulses at a predetermined frequency;
• counter means functionally connected to said USART and responsive to said clock signal by counting said pulses for providing a count signal indicating that a predetermined number of bytes of said parallel data has been received, and responsive to said control signal for clearing said count signal;
• and
• interface means functionally connected to said counter means and responsive to provision of said count signal for instructing said data communications device to halt the transmission of said serial data.

A method for controlling the flow of serial data from a data communications device to a host device when using a universal synchronous-asynchronous receiver transmitter (USART) to convert said serial data from said data communications device to parallel data for said host device, said USART providing clock pulses at a predetermined frequency, having a buffer for the temporary storage of said parallel data, and providing a control signal when said buffer is empty, said method preventing the loss of said data, comprising the steps of:

• counting said clock pulses;
• providing a count signal responsive to the number of said clock pulses exceeding a predetermined value;
• clearing said count signal in response to provision of said control signal;
• and
• responding to provision of said count signal by instructing said data communications device to halt the transmission of said serial data.

In a system comprising a host device, a serial communications device containing a universal synchronous-asynchronous receiver transmitter (USART), and a remote transmitter for sending the data to said host device by way of said serial communications device, said USART converting said data from a serial format into a parallel format, providing clock pulses at a predetermined rate, having a buffer for the temporary storage of said data and providing a first signal when said buffer is empty, an improvement to said serial communications device to prevent said buffer from overflowing by automatically signaling said remote transmitter to stop transmission of said data, comprising:

• first means for setting a pulse count to a first predetermined value in response to said first signal, for counting said clock pulses, and providing a second signal when said pulse count reaches a second predetermined value;
• second means responsive to provision of said second signal for rendering said first means non-responsive to said clock pulses;
• and
• third means responsive to provision of said second signal for providing a control signal to said remote transmitter to signal said remote transmitter to stop said transmission of said data.