Using MAX6954 to drive a 7-segment LED display

　　The configuration register (0x04) is used to set the entry and exit of shutdown mode, control the flashing function, globally clear each bit of data, and select whether to control the brightness of each bit globally or individually. The configuration register contains 7 bits (see Table 3).

　　The S bit is used to select shutdown mode or normal operating mode (read/write).

　　Bit B is used to select the blink rate (read/write).

　　The E bit is used to globally enable or disable the flashing function (read/write).

　　The T bit is used to reset the flash sequence (this data is not stored - transient bit).

　　The R bit is used to globally clear the P0 and P1 two-level registers corresponding to all display bits (this data is not stored - transient bit).

　　The I bit is used to select whether to control the brightness of each bit globally or individually (read/write).

　　The P bit returns the current blink timing phase (read-only—writing a value to this bit will be ignored).

　　Table 3. Configuration register format CONFIGURATION


　　Start the display driver by writing 0x01 to register 0x04, and at the same time set the working mode to global brightness control and disable flickering. The internal oscillator starts when the MAX6954 exits shutdown mode, and the oscillator output pin is OSC_OUT. Note that when the power-on status of data control registers 0x60 to 0x67 is 0x20 or no segments are lit, the 7-segment display remains blank (see Table 2 and Figure 3).

　　　　　　　　　　　
　　　　　　　　　　　　　　Figure 3. 7-segment display font

　　MAX6954 has a built-in hexadecimal font for 7-segment display, using 7 bits to represent hexadecimal characters, and the 8th bit is used to select whether to light the decimal point (DP) (see Table 4) . The data register has two levels, P0 and P1. Each display bit is represented by 2 bytes in memory, one byte is located in P0 and the other is located in P1 (see Table 7). The data register is a mapped address, so each bit of data can be updated in P0 (register 0x20 to 0x2F), or in P1 (register 0x20 to 0x4 F), or both levels can be updated simultaneously (register 0x60 to 0x67). The data in the data register does not directly control the display of each segment in the 7-segment display. Instead, it is used to address the character generator that stores 7-segment word pattern data (see Figure 3). The lower 7 bits of register data (D6 to D0) are used to select characters from the font. The highest bit (D7) controls the decimal point (DP) display; setting it to 1 will display DP, and setting it to 0 will not display DP.

　　Table 4. Numeric type data register format

　　If the flash function is disabled by the flash enable bit E of the configuration register (see Table 3), the data in the data register in P0 is used for display multiplexing. The data in the data register in P1 is not used. If the blink function is enabled, the data multiplexing displays in P0 and P1 are used alternately. The data in P0 and P1 are respectively applied to different phases of the alternating changes of the flashing clock, thereby multiplexing the LED display to achieve the flashing function.

　　The following is an example of using the MAX6954 driver to display the Maxim/Dallas Sales Department phone number: 1 800 629 4642. Set the configuration register to disable the flash function, so that data bits 0 to 7 can be controlled respectively by writing data to registers 0x20 to 0x2F. Use the font pattern in Figure 3 to get the code corresponding to each character.

　　 Table 5. Telephone 800.629.4642 Example
　　　　

　　Adjust the display brightness by writing data to register 0x02 (global brightness control register). The brightness can be adjusted between 0x00 (minimum brightness, 1/16 current) and 0xFF (maximum brightness, 15/16 current). The brightness of each bit can also be controlled individually. Refer to the MAX6954 data sheet for details on display brightness adjustment and other advanced features such as GPIO and key scanning.

　　Table 6. Routine command set REGISTER

　　
　　　Table 7. Partial register address map of MAX6954/MAX6955?
　　
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