Pulse or digital communications – Synchronizers – Frequency or phase control using synchronizing signal
Reexamination Certificate
1998-04-08
2001-05-29
Pham, Chi (Department: 2631)
Pulse or digital communications
Synchronizers
Frequency or phase control using synchronizing signal
Reexamination Certificate
active
06240151
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C §119 from an application entitled Method For Transmitting And Receiving Asynchronous Serial Data In Digital Signal Processor earlier filed in the Korean Industrial Property Office on Apr. 8, 1997, and there duly assigned Serial No. 97-12794 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a serial data communicating method, and more particularly, to a method for asynchronously transmitting and receiving data using a serial port of a digital signal processor (DSP).
2. Background Art
A 32-bit floating point processor such as the TMS320C30 digital signal processor (DSP) by Texas Instruments (TI®) is a dedicated digital processor which has been widely used in a servo controller and for image processing. A general digital signal processor has a serial port or a parallel port to transmit and receive data to and from another processor. The TMS320C30 DSP has a synchronous serial communication port, and performs asynchronous serial communication with another TMS320C30 DSP at high speed through the serial communication port.
In general, it would be convenient if the DSP serial port could be connected to a general-purpose system such as a personal computer (PC) or a notebook computer. For instance, a program coded on a PC can be downloaded to the DSP, or data of the DSP can be continuously logged by a PC during the operation of the DSP system. If the output values of a controller of a servo system using DSP are logged and then analyzed by a PC, an optimal controller could be easily realized. Also, a notebook computer could issue an operation command to a DSP system so that the DSP system could perform a specific operation, whereby a simple emulation may be performed. That is, an external system could be tested irrespective of the working place and equipment, if the DSP serial port could be connected to a general-purpose system.
Currently, however, the DSP can not perform data communication with a general purpose computer system such as a PC or a notebook PC in a serial communication method using a serial port of the DSP. Therefore, a special asynchronous communication method is required to realize serial communication with the general-purpose computer system. Asynchronous data reception is discussed in U.S. Pat. No. 5,155,486 to Philip J. Murfet et al. entitled Asynchronous Serial Data Receiver With Capability For Sampling The Mid-Point Of Data Bits and U.S. Pat. No. 5,623,522 to Masahiro Ito entitled Asynchronous Serial Data Receiving Device. The asynchronous communication, however, needs some hardware and software, because of the fact that asynchronous data begins with a start bit which is not part of the actual data. That is, the start of reception of data is recognized using the start bit, and the following bits are read according to the value of a reception timer counter register. Also, upon transmission of data, the bits are transmitted one by one using a transmission timer counter register.
Through a communication experiment, I have found that the transmission and reception timer counters in the TMS320C30 DSP perform a continuous counting operation in synchronization with a clock pulse of a processor, regardless of whether serial communication is performed or not. Accordingly, the values of the transmission and reception timer counters s are not consistent at the point of time when the start bit is transmitted or received, which causes a communicational failure during lengthy communications.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for transmitting and receiving data using a serial port of a DSP, whereby a communication error can be prevented by resetting the value of a reception timer counter to a predetermined value whenever a start bit is received when receiving asynchronous data transmitted via a serial port, in order to have data read at the middle point of a pulse section for each bit of a data signal, and a pulse section per bit of a transmission signal is adjusted and transmitted by resetting a transmission timer counter to zero at the beginning point of transmission of the start bit during data transmission.
To accomplish the above object, there is provided a method of asynchronously receiving serial data via a serial port of a TMS320C30 DSP including: a reception timer period register for storing pulse section information representing how many clock pulses correspond to one bit of the serial data, when a 1-bit time section of the transmitted serial data is expressed as a pulse section composed of a plurality of clock pulses; and a reception timer counter for counting the clock pulses up to a value determined by the reception timer period register, resetting the counted value to zero, and counting again starting from zero, the method comprising the steps of: determining whether a start bit is received; enabling the serial port when the received start bit falls from high to low; setting the initial value of the reception timer counter to half the value in the reception pulse section register, when the serial port is enabled; receiving one bit of data whenever the value of the reception timer counter becomes equal to the value in the reception timer period register, until a stop bit is received; and disabling the serial port when the stop bit is received.
Additionally, there is provided a method of asynchronously transmitting serial data via a serial port in a TMS320C30 DSP including: a transmission timer period register for storing pulse section information representing how many clock pulses correspond to one bit of the serial data, when a 1-bit time section of the transmitted serial data is expressed as a pulse section composed of a plurality of clock pulses; and a transmission timer counter for counting the clock pulses up to a value determined by the transmission timer period register, resetting the counted value to zero, and counting again starting from zero, the method comprising the steps of: generating transmission data by adding start and stop bits to the beginning and end of a portion of the data to be transmitted, to make asynchronous data; initializing the transmission timer counter to zero at the point in time when the start bit is transmitted; transmitting one bit of data, whenever the value of the transmission timer counter becomes equal to the value in the transmission timer-period register; and repeating the step of transmitting one bit until the stop bit is transmitted.
REFERENCES:
patent: 5155486 (1992-10-01), Murfet et al.
patent: 5623522 (1997-04-01), Ito
patent: 62-20451 (1987-01-01), None
patent: 62-81840 (1987-04-01), None
patent: 63-238745 (1988-10-01), None
patent: 3-85043 (1991-04-01), None
Texas Instruments, TMS320C30 Digital Signal Processor, Apr. 1996, Revised Jun. 1997, pp. 1-53.
Burd Kevin M
Bushnell , Esq. Robert E.
Pham Chi
Samsung Electronics Co,. Ltd.
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