Read Data From Cg Ram Or Dd Ram; Operation; Four-Bit Data Interface - Xilinx Spartan-3A User Manual

Chapter 5: Character LCD Screen
After the write operation, the address is automatically incremented or decremented by 1
according to the
Execution Time: 40 μs

Read Data from CG RAM or DD RAM

Reads data from DD RAM if the command follows a previous
command, or reads data from CG RAM if the command follows a previous
Address
After the read operation, the address is automatically incremented or decremented by 1
according to the
during read operations.
Execution Time: 40 μs

Operation

The board has an eight-bit data interface to the character LCD. Other Xilinx boards use a
four-bit interface. As shown in
both an eight-bit and a four-bit interface for compatibility reasons. Many existing reference
designs are already built around a four-bit interface.

Four-Bit Data Interface

Figure 5-6
for setup, hold, and enable pulse length relative to the 50 MHz clock (20 ns period)
provided on the board.
52
Entry Mode Set command. The entry mode also determines display shift.
command.
Entry Mode Set command. However, a display shift is not executed
Figure
illustrates a write operation to the LCD, showing the minimum times allowed
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Set DD RAM Address
5-1, the Spartan-3A/3AN Starter Kit board supports
Spartan-3A/3AN Starter Kit Board User Guide
R
Set CG RAM
UG334 (v1.0) May 28, 2007