Abstract:
A monitor having a microcomputer for performing a serial peripheral interface (SPI) communication with a personal computer (PC) which can improve the communicability between the PC and the monitor. The monitor includes an interface using in common one communication type utilizing a serial clock and a serial data through a printer port of the PC and the other communication type utilizing RS232C through a COM port of the PC, and data is stored in or read out from the microcomputer through the interface. The interface performs an input/output of the serial data utilizing the printer port and the COM port.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an interface of a monitor communicating with a personal computer (PC), and more particularly to an interface of a monitor which can input/output serial data through a printer port and a COM port simultaneously by providing a communication interface utilizing the printer port of the PC communicating with a microcomputer of the monitor, thereby improving communicability between the PC and the microcomputer of the monitor. 
     2. Description of the Related Art 
     As shown in FIG. 1, the conventional interface of a monitor communicating with a PC comprises a microcomputer  1  of the monitor for processing data by serial peripheral interface (SPI) communication, a printer port  3 A, installed on the rear part of the PC  3 , for inputting/outputting print data signals, and an interface section  2 , connected between the printer port  3 A and the microcomputer  1 , for inputting/outputting data therethrough. 
     The interface section  2  comprises an inverter G 1 , connected between pin No.  2  of the printer port  3 A of the PC  3  and a serial clock line (SCL) terminal of the microcomputer  1 , for transmitting a clock line control signal, an inverter G 2 , connected between the SCL terminal of the microcomputer  1  and pin No.  15  of the printer port  3 A of the PC  3 , for checking the status of a clock signal transmitted from the inverter G 1  to the microcomputer  1 , an inverter G 3 , connected between pin No.  3  of the printer port  3 A of the PC  3  and a serial data line (SDL) terminal, for transmitting a data line control signal, and a inverter G 4 , connected between the SDL terminal of the microcomputer  1  and pin No.  10  of the printer port  3 A of the PC  3 , for checking the status of data signal transmitted from the inverter G 3  to the microcomputer  1 . 
     The reference numberals R 1  to R 4  in FIG. 1 denote pull-up resistors. 
     The operation of the conventional interface of a monitor communicating with a PC will be explained. 
     First, in case that the PC  3  writes data into the microcomputer  1  through the clock line and the data line, the pin Nos.  2  and  3  of the printer port  3 A of the PC  3  are initialized with ‘high’ level signals. At an initial stage, as illustrated in FIG. 2A, the starting condition of the data transmission is given at the point where the clock line and the data line go from a ‘high’ state to a ‘low’ state. At this time, the microcomputer  1  acknowledges that the PC  3  starts data reading on writing operation by detecting the starting condition through the clock line and data line. 
     In case of writing the data in the microcomputer, the PC  3  outputs data through the inverter G 3 , synchronizing the data with the clock signal applied to the inverter G 1  of the interface section  2 . The microcomputer  1  of the monitor then receives and stores in a built-in memory the clock signal and the data inputted from the inverters G 1 , G 3 . Meanwhile, in case of reading the data from the microcomputer  1 , the PC  3  reads necessary data through the inverters G 2 , G 4  form the microcomputer  1 . 
     At this time, the PC  3  feeds back the data and the clock signal outputted from the inverters G 1 , G 3  through the inverters G 2 , G 4  of the interface section  2  to check whether or not the current clock line and the data line operate in a normal state. Also, the PC  3  acknowledges the read data by recognizing the clock inputted/outputted through the inverter G 3 . Specifically, the PC  3  transmits or reads the data byte by byte by acknowledging the rising edge of the ninth clock of the clock signal. At this time, the microcomputer  1  of the monitor displays the inputted/outputted data on the monitor screen so that the user can see the data. 
     If the stop condition is inputted as shown in FIG. 2A during the above-described data input/output operation, the PC  3  terminates the data input/output operation. 
     However, according to the conventional interface of a monitor communicating with a PC, the PC cannot perform a data communication with the microcomputer through the printer port if the printer cable is connected to the printer port of the PC, thereby decreasing the usability of the system. Also, it is impossible to compatibly perform a serial communication or parallel communication using the input/output ports of the PC, thereby greatly deteriorating the operability of the system. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to solve the problems involved in the prior art, and to provide an interface of a monitor communicable with a PC which can input/output serial data simultaneously utilizing a COM port in parallel with the printer port of the PC, thereby improving the communicability between the PC and the microcomputer of the monitor. 
     In one aspect of the present invention, there is provided a monitor having a microcomputer for performing a SPI communication with a PC, the monitor comprising an interface using in common one communication type utilizing a serial clock and a serial data through a printer port of the PC and the other communication type utilizing RS 232 C through a COM port of the PC, wherein data is stored in or read out from the microcomputer through the interface. 
     In another aspect of the present invention, there is provided an interface of a monitor communicating with a PC, the monitor having a microcomputer for controlling input/output of parallel and serial data through the microcomputer and a D-sub connector for connecting the parallel and serial data, and the PC having a COM port for inputting/outputting the serial data by the RS 232 C and a printer port for inputting/outputting print data, the interface comprising: 
     a parallel communication section, connected between the printer port and the COM port of the PC and the D-sub connector of the monitor with parallel communication lines, for inputting/outputting data; 
     a serial switch, connected between the COM port and the D-sub connector, for switch-controlling the communication lines to effect a serial communication; and 
     a transistor, connected to one side of the D-sub connector, for providing an interrupt switching signal to the microcomputer when the serial communication is effected. 
     In still anther aspect of the present invention, there is provided a communication interface in a display device having a processor for performing a serial interface communication with a computer, the communication interface comprising: 
     a serial port connector coupled to the processor and connectable to a serial port of the computer; 
     a parallel port connector coupled to the processor and connectable to a parallel port of the computer; and 
     a switch operable to switch communication to the processor between the serial port when communication through the serial port is desired and the parallel port when communication through the parallel port is desired. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above object, other features and advantages of the present invention will become more apparent by describing the preferred embodiment thereof with reference to the accompanying drawings, in which: 
     FIG. 1 is a block diagram illustrating the conventional interface of a monitor communicating with a PC. 
     FIG. 2A is a waveform diagram illustrating the clock signal and data generated through the clock line and the data line for SPI communication. 
     FIG. 2B is a waveform diagram illustrating the waveform generated from the COM port for RS 232 C communication according to the present invention. 
     FIG. 3 is a block diagram of an interface of a monitor communicating with a PC according to the present invention. 
     FIG. 4A is a schematic circuit diagram of the construction for controlling the display state under the control of a microcomputer of the monitor utilizing a serial clock and serial data through a printer port of the PC. 
     FIG. 4B is a schematic circuit diagram of the construction for controlling the display state under the control of a microcomputer utilizing a COM port of the PC according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 3,  4 A and  4 B show an interface of a monitor for performing communication with a PC. 
     Referring to FIG. 3, the interface of the monitor for performing communication with a PC is connected between the monitor  30  having a D-sub connector (D-type miniature sub-connector)  20  for connecting parallel and serial data inputted to/outputted from a microcomputer of the monitor and the PC  40  having a COM port  40 A for inputting/outputting the serial data and a printer port  40 B for inputting/outputting printer data. The interface includes a parallel communication section  50 , connected between the printer port  40 B provided on the rear of the PC  40  and the COM port  40 A for the RS 232 C communication, and the D-sub connector  20  provided on the rear of the monitor with parallel communication lines, for inputting/outputting data; a serial switch SW 1 , connected between the COM port  40 A and the D-sub connector  20 , for switch-controlling the communication lines to effect a serial communication; and a transistor Q 11 , connected to one side of the D-sub connector  20 , i.e., pin No.  5 , as shown in FIG. 4B, for providing an interrupt switching signal to the microcomputer  10  when the serial communication is effected. 
     The parallel communication section  50  includes an inverter G 1  connected between pin No.  2  of the printer port  40 B of the PC  40  and pin No.  15 , which is a terminal of serial clock line of the D-sub connector  20 , for transmitting a signal to control the clock line; an inverter G 2  for feeding back the status of the clock signal transmitted from the inverter G 1  to the microcomputer; an inverter G 3  connected between pin No.  3  of the printer port  40 B of the PC  40  and pin No.  12 , which is a terminal of serial data line (SDL), of the D-sub connector  20  for transmitting the signal to control data line; and an inverter G 4  connected between the SDL terminal of the D-sub connector  20  and pin No.  10  of the printer port  40 B of the PC  40  for feeding back the data signal transmitted form the inverter G 3  to the microcomputer to check the data signal. 
     The serial switch SW 1  is connected between pin No.  3  of the COM port  40 A and pin No.  5  of the D-sub connector  20  to perform switching operation for serial communication. On the rear face of the PC  40 , a PC input port  40 C is connected to the respective terminal pins of the D-sub connector  20  for transmitting an image signal and a synchronous signal from the PC  40 . An SCL terminal and an SDA terminal of the microcomputer are connected between the pin No.  15  and pin No.  12 , as shown in FIG.  4 A. Also, the D-sub connector  20  is connected to the PC input port  40 C for inputting/outputting the image signal and the synchronous signal. A switch SW 2  is provided between pin No.  9  of the D-sub connector  20  and pin No.  9  of the PC input port  40 C for writing data on a display data channel (DDC). 
     The pin No.  5  of the COM port  40 A is connected to ground. The reference numerals R 1  to R 14  denote resistors. 
     Operation of the interface of a monitor communicating with PC as constituted above according to the present invention will now be explained with reference to FIGS. 3,  4 A and  4 B. 
     FIG. 3 shows writing of serial data to the microcomputer by means of the parallel communication section  50 . When transmitting a horizontal size control signal with serial data through the microcomputer of the monitor  30 , the PC  40  determines the horizontal size value inputted by the user, and converts the resultant horizontal control signal into a transmitting format as illustrated in FIG. 2A to transmit the signal to the microcomputer of the monitor  30  through the inverter G 1  and inverter G 3  of the parallel communication section  50 . In other words, the PC  40  inputs the clock signal to the inverter G 1  connected to the pin No.  2  of the printer port  40 B, while inputting serial data in response to the horizontal size control signal, which is synchronized with the clock applied to the inverter G 1 , through the inverter G 3  connected to the pin No.  3 . Accordingly, the serial data inputted to the inverter G 3  of the parallel communication section  50  are inputted to the SDA terminal of the microcomputer through the pin No.  12  of the D-sub connector  20  of the monitor  30  as illustrated in FIG.  4 A. At the same time, the serial clock signal inputted to the inverter G 1  of the parallel communication section  50  is inputted to the SCL terminal of the microcomputer of the monitor  30  through the pin No.  15  of the D-sub connector  20  of the monitor  30  as illustrated in FIG.  4 A. The microcomputer of the monitor  30  then decodes the serial data in response to the inputted horizontal size control signal to input the horizontal size control signal to the horizontal size control circuit section (not illustrated). The horizontal size control circuit section controls a pulse width modulation (PWM) value in response to the horizontal size control signal of the microcomputer to adjust the horizontal size. 
     On the other hand, when reading the serial data from the microcomputer by means of the parallel communications section  50 , the microcomputer transmits the serial clock and the data to the inverter G 2  and inverter G 4  of the parallel communication section  50  through the SDA line and SCL line of the D-sub connector  20 , respectively, and the PC  40  reads the serial clock and the data form the inverter G 2  and the inverter G 4 . 
     Meanwhile, the PC  40  feeds back the data and the clock signal outputted from the inverter G 1  and the inverter G 3  through the inverter G 2  and the inverter G 4  of the parallel communication section  50  to determine whether the present clock line and the data line operate in normal status. If the PC  40  and the monitor  30  are determined to operate in normal status, an image signal and a synchronous signal are inputted through the PC input port  40 . 
     Meanwhile, when performing serial communication by means of the COM port, the user must switch on the serial switch SW 1 , and set a signal to control the horizontal size. Then, the PC  40  converts the serial data according to the horizontal size into the transmitting format as illustrated in FIG. 2B, and outputs the serial data through the pin No.  3  of the COM port  40 A. The serial data outputted from the pin No.  3  of the COM port  40 A are inputted to the pin No.  5  of the D-sub connector via the serial switch SW 1 . The serial data are then inputted to the base terminal of the transistor Q 11  connected to the pin No.  5  of the D-sub connector  20 . The transistor Q 11  is subsequently switched on, and the serial data of RS 232 C are inputted to the interrupt terminal of the microcomputer. 
     At this stage, the microcomputer performs detection starting from the edge point at which the initial interval of the inputted serial data decreases from the value ‘high’ to the value ‘low’ as shown in FIG.  2 B. The microcomputer subsequently generates an interrupt according to the starting condition of the serial data, and decodes the remaining serial data to input the horizontal size control signal to the horizontal size control circuit section (not illustrated). 
     The horizontal size control circuit section controls the PWM value in response to the horizontal size control signal of the microcomputer to adjust the horizontal size (PWMO-PWMN). 
     Thus, according to the present invention, serial data can be transmitted by means of the printer port  40 B which performs parallel communication. RS 232 C communication can also be performed by means of the COM port  40 A. 
     As described above, the present invention results in an effect of improving communicability between a PC and a monitor by realizing an interface for communication which utilizes a COM port as well as a printer port to communicate with a microcomputer of the monitor, and inputs/outputs serial data through the printer port and the COM port simultaneously. 
     While the present invention has been described and illustrated herein with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.