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7/30/2019
Basys MX3 Reference Manual [Reference.Digilentinc]
https://reference.digilentinc.com/reference/microprocessor/basys-mx3/reference-manual?_ga=2.68739409.1349070004.1564406803-1961480359.…
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The board also provides a switch to turn on and off the LCD () display backlight, situated on the bottom right corner of the LCD () display.
The LCD () display is controlled by a set of commands written to the device. Also, read commands provide the ability to read status and
data. Please read the SD1602H datasheet for a detailed list of read and write commands. The LCD () display requires a specific initialization
sequence, also detailed in the datasheet.
The device features two types of memory: CGRAM and DDRAM.
The LCD () controller contains a character-generator ROM () (CGROM) with
192 preset 5×8 character patterns
hold 80 character codes. Character codes written into the DDRAM serve as indexes into the CGROM (or CGRAM). Writing a character
code into a particular DDRAM location will cause the associated character to appear at the corresponding display location. Display positions
can be shifted left or right by setting a bit in the Instruction Register (IR). The write-only IR directs display operations (such as clear display,
shift left or right, set DDRAM address, etc). A busy flag shows whether the display has competed the last requested operation; prior to
initiating a new operation, the flag can be checked to see if the previous operation has been completed.
The display has more DDRAM locations (2*40) than can be displayed at any given time (2*16). DDRAM locations 00H to 27H map to the
first display row, and locations 40H to 67H map to the second row. Normally, DDRAM location 00H maps to the upper left display corner
(the “home” location), and 40H to the lower left. Shifting the display left or right can change this mapping. The display uses a temporary
data register (DR) to hold data during DDRAM /CGRAM reads or writes, and an internal address register to select the RAM () location.
Address register contents, set via the Instruction Register, are automatically incremented after each read or write operation. The LCD ()
display uses ASCII () character codes. Codes up through 7F are standard ASCII () (which includes all “normal” alphanumeric characters).
Codes above 7F produce various international characters.
The following timing diagrams detail how write and read process must be implemented. The essential difference is the polarity of the
DISP_RW signal (0 for write and 1 for read). For more detailed timing information, refer to the KS0066U datasheet.