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Motor de Búsqueda de Datasheet de Componentes Electrónicos |
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Motor de Búsqueda de Datasheet de Componentes Electrónicos |
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MC145220 Datasheet(PDF) 11 Page - Motorola, Inc |
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MC145220 Datasheet(HTML) 11 Page - Motorola, Inc |
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11 / 54 page  MC145220EVK 11 MOTOROLA EXTERNAL REFERENCE INPUT To use an external reference, disconnect J3, J4, J13, and J14. Use a reference signal at J2 which com- plies with data sheet requirements. Then modify the reference frequency in the program main menu to reflect the changes made (F menu item). DATA TRANSFER FROM COMPUTER TO EVK To control the serial input EVK with the parallel printer port, a conversion is done. Printer cards are de- signed to output eight bits through eight lines. A bit mask is used to obtain the bit combination for the three required output lines (Data, Clock, Load). As bytes are sent to the printer card in sequence, it ap- pears to be a serial transfer. The printer port is used because data transfer using the serial port would be much slower. A standard IBM PC can support a parallel port data rate of 4.77 MHz. IBM PCs and compatibles can accept up to three printer port configurations. These ports are called LPT1, LPT2, and LPT3. Each printer port has a unique address. Two sets of addresses are in common use. One set applies to IBM PC XT, AT, and clones. The other is for the PS 2 line. To load data into the EVK, the correct address must be selected. The program default is $278. If $278 is not the address in use, it must be modified by entering the P menu item in the main menu. All allowed addresses given in hexadecimal are as follows: Label IBM PC and Clones PS 2 LPT1 278 3BC LPT2 378 378 LPT3 3BC 278 Up to three EVK boards can operate independently from one printer port. All lines on the printer port are connected to every EVK. Even with three boards operating, only three output lines (Clock, Data, and Load) from the printer card are used. If two boards are controlled together, data for the second board is received from the Output A of the first. Output A is a configurable output on ’220 devices, which in this case is used to shift data through chip 1 into chip 2. Output A and Data are connected using a printer port input line. This was done to avoid connecting extra wires. Fortunately not all port input lines are needed for computer input. Load and Clock are common to both boards. A three–board cascade is handled similarly to a two–board cascade. Out A on the first board is fed to Data on the second. Out A on the second connects to Data on the third. Instructing the program on the quantity of boards connected together allows it to modify the number of bits sent. All boards have a DIP switch S1 which gives each a unique address. The configuration menu is used to tell the program what type of board is connected at a board address. Switch positions for all possible addresses are given in Figure 3. |
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Descripción similar - MC145220 |
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