Parallel to serial asynchronous hardware assisted DSP interface

• US 6,378,011 B1
• Filed: 05/28/1999
• Issued: 04/23/2002
• Est. Priority Date: 05/28/1999
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Moore, David, Messerly, Shayne
• Primary Examiner(s): Lee, Thomas
• Assistant Examiner(s): KIM, HAROLD J
• Application Number:
  US09/322,744
• Time in Patent Office: 1,061 Days
• Field of Search: 710/70, 710/71, 710/38, 710/22, 370/280, 379/59, 379/98, 455/454, 455/557
• US Class Current: 710/71
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices

Abstract

Parallel data is serialized and transmitted and asynchronous data is received and placed into parallel bytes using a hardware assisted interface. The interface can be driven with very little overhead to the DSP. Additional timing registers and enhanced data buffers decrease the necessary DSP resource commitment. Furthermore the hardware settings in the interface can be adjusted by the DSP to optimize the interface'"'"'s performance in transmitting various asynchronous protocols.

Claims

1. A serial data apparatus for converting parallel data generated by a digital signal processor (DSP) into asynchronous serial data bytes according to an asynchronous protocol specified by the DSP and in a separate pipeline converting asynchronous serial data to synchronous parallel data, the apparatus comprising:

a register module;

a receive data FIFO digitally connected to the register module;

a transmit data FIFO digitally connected to the register module;

a DSP interface digitally connected to the register module comprising a bidirectional control signal bus, a bidirectional DSP data bus, and a read only status bus;

a timing control interface digitally connected to the register module, the receive data FIFO, and the transmit FIFO;

a asynchronous serial data out (ASDO) pin digitally connected to the timing control interface; and

a asynchronous serial data in (ASDI) pin digitally connected to the timing control interface.

2. The apparatus as in claim 1, wherein the register module includes a status register which contains transmission and reception status flags represented as individual bits in the register thereby providing the DSP with status information with one read.

3. The apparatus as in claim 2, wherein the register module further comprises a control register giving the DSP control to initialize the transmit data FIFO and the receive data FIFO, as well as enabling all data transmissions to the apparatus and data receptions from the apparatus.

4. The apparatus as in claim 3, wherein the apparatus provides the DSP with critical timing information necessary for the DSP to pace serial data being sent, thereby allowing the DSP to communicate with devices that do not use standard asynchronous serial communication methods.

5. The apparatus as recited in claim 4, wherein the timing control interface performs pacing and serialization through control of the receive data FIFO and transmit data FIFO without direct DSP intervention.

6. The apparatus in claim 5, wherein the apparatus further comprises an EEPROM control module that eliminates the need for the DSP to run the communication protocols necessary to program the EEPROM, said EEPROM control module being readable and writable by the register module or DSP.

7. The apparatus as in claim 6, wherein the receive data FIFO and the transmit data FIFO are 128×

8 two port FIFO memory modules.

8. An electronically integrated high throughput asynchronous serial data input/output interface comprising:

a register module comprising an interrupt generator, a serial data control register, a serial data status register, a baud rate generator register, a receive stale count register, a transmission fill level register, a receive fill level register, a transmission FIFO threshold register, and a receive FIFO threshold register;

a transmit FIFO buffer electronically connected to said register module, the transmit FIFO buffer being selectively adjusted in defined useable size for efficient asynchronous data transfers between a processor and a serial transmission line;

a receive FIFO buffer electronically connected to said register module, the receive FIFO buffer being selectively adjusted in defined useable size for efficient asynchronous data transfers between a serial transmission line and a processor;

an asynchronous transmit control module electronically connected to said transmit FIFO buffer and said register module;

an asynchronous receive control module electronically connected to said receive FIFO buffer and said register module.

9. The interface as in claim 8, wherein said processor is a digital signal processor (DSP) and the transmit FIFO threshold register and receive FIFO threshold register contain values for selectively adjusting the defined useable size for efficient communication between the DSP and the serial transmission lines, such that the adjustment involves minimizing overhead of the DSP specifically associated with a selected asynchronous protocol.

10. The interface as in claim 8, wherein the serial data status register provides single clock cycle access for communication related bit flags from the interface comprising:

a transmit FIFO empty flag set when the transmit FIFO is empty;

a transmit FIFO threshold flag that is set when the number of characters in the transmit FIFO is less than or equal to a transmission threshold value, thereby signally the preselected level that the processor should begin to refill the transmit FIFO;

a transmit FIFO full flag that is set when the transmit FIFO is full, depending on the asynchronous protocol being used, this will either create a buffer overflow interrupt or it will send an interrupt to the processor to stop sending data to the FIFO until there is room as well as sending an enable transmission signal to the asynchronous transmit control module until the transmit threshold flag is set;

a receive FIFO empty flag set when the receive FIFO is empty;

a receive FIFO threshold flag that is set when the number of characters in the receive FIFO is greater than the receive threshold value, thereby signally the preselected level that the processor should begin to empty the receive FIFO;

a receive FIFO Full flag that is set when the receive FIFO is full, depending on the asynchronous protocol being used, this will either create a buffer overflow error or send an interrupt to the processor to empty the FIFO along with a disable receive signal to the asynchronous receive control module until the receive FIFO threshold flag is cleared; and

a receive character time out flag, set when no characters have been removed from the Receive FIFO for a time period equal to the bit transfer rate times the value store in the stale count register and there is one or more characters in the FIFO.

11. The interface as in claim 8, where in the interface further comprises a hardware timer electronically connected to said register module, said hardware timer assisting the interface with timing critical operations and may be used by the DSP to time slow serial data communications when the proper asynchronous protocol has not been performed, thereby allowing the interface to continue its effectiveness by minimizing overhead of the DSP even with non-standard asynchronous protocols.

12. The interface as in claim 8, wherein the serial data control register provides the DSP with selective FIFO reset control, as well as the ability to selectively enable transmission, reception, and hardware timing with one write operation.

13. The interface as in claim 8, said interface further comprising a EEPROM Control module containing a hardware implementation of the DSP code needed to program the EEPROM with communication protocols.

14. In a computer system including a modem with a parallel to serial asynchronous hardware assisted DSP interface, a method of communication that converts asynchronous digital cellular data into parallel synchronous data for the DSP and converts parallel synchronous data from the DSP into asynchronous serial data frames for transmission across a digital cellular communication line, the communication method comprising the steps of:

receiving asynchronous data into the interface and transmitting the data to the DSP in a parallel synchronous fashion;

receiving synchronous parallel data and sending the data in accordance with an established asynchronous transfer rate and method;

said receiving asynchronous data into the interface and said transmitting data to the DSP step including the steps of;

receiving the asynchronous data from the digital cellular phone;

storing the data in a parallel fashion in a buffer until an appropriate threshold value is reached;

sending a threshold interrupt to the DSP;

reading parallel data a threshold number of times from the buffer;

said receiving synchronous data and said sending asynchronous data including the steps of;

writing a single parallel data byte to the interface;

placing the data in an interface buffer;

sending the data in accordance with an establish asynchronous protocol at an established transfer rate.