Cg Rom - Xilinx Spartan-3A User Manual

Chapter 5: Character LCD Screen
The
writing to DD RAM. Write DD RAM data using the
command, and read DD RAM using the
The DD RAM address counter either remains constant after read or write operations, or
auto-increments or auto-decrements by one location, as defined by the I/D set by the
Mode Set

CG ROM

The Character Generator ROM (CG ROM) contains the font bitmap for each of the
predefined characters that the LCD screen can display, shown in
code stored in
the CG ROM. For example, a hexadecimal character code of 0x53 stored in a
location displays the character 'S'. The upper nibble of 0x53 equates to DB[7:4] = 0101
binary and the lower nibble equates to DB[3:0] = 0011 binary. As shown in
character 'S' appears on the screen.
English/Roman characters are stored in CG ROM at their equivalent ASCII code
addresses.
46
Set DD RAM Address command initializes the address counter before reading or
command.
DD RAM for each character location subsequently references a position with
www.xilinx.com
Write Data to CG RAM or DD RAM
Read Data from CG RAM or DD RAM
Figure
Spartan-3A/3AN Starter Kit Board User Guide
UG334 (v1.0) May 28, 2007
R
command.
Entry
5-4. The character
DD RAM
Figure 5-4, the