PEDL9040A-03
¡ Semiconductor
ML9040A-Axx/-Bxx
Character Generator RAM (CG RAM)
The CG RAM is used to display user's original character patterns other than character
patterns in the CG ROM.
The CG RAM has a capacity (64 bytes = 512 bits) of writing 8 kinds of characters for 5 x 7
dots and 4 kinds of characters for 5 x 10 dots.
When displaying character patterns stored in the CG RAM, write 8-bit character codes (00
to 07 or 08 to 0F; hex.) on the left side as shown in Table 2. Then it is possible to output the
character pattern to the LCD display position corresponding to the DD RAM address.
The following explains how to write and read character patterns to and from the CG RAM.
(1)When the character pattern is 5 x 7 dots (see Table 3-1).
• A method of writing character pattern to the CG RAM by CPU:
Three bits of CG RAM addresses 0-2 correspond to the line position of the character
pattern.
First, set increment or decrement by the CPU, and then input the CG RAM address.
After this, write character patterns to the CG RAM through DB - DB line by line.
0
7
DB to DB correspond to CG RAM data 0-7 in Table 3-1.
0
7
It is displayed when "H" is set as input data and is not displayed when "L" is set as
input data.
Since the ADC is automatically incremented or decremented by 1 after the writing of
data to the CG RAM, it is not necessary to set the CG RAM address again.
The line, in which the CG RAM addresses 0-2 are all "H" ("7" in hexadecimal
notation), is the cursor position. It is ORed with the cursor at the cursor position and
displayed to LCD.
For this reason, it is necessary to set all input data that become cursor positions to "L".
Although CG RAM data 0-4 bits are output to the LCD as display data, CG RAM data
bits 5-7 are not output. The latter can be written and read to and from the RAM, it
is therefore allowed to be used as data RAM.
• A method of displaying the CG RAM character pattern to the LCD:
The CG RAM is selected when upper 4 bits of the character codes are all "L".
As character code bit 3 is invalid, the display of "0" in Table 3-1, is selected by
character code "00" (hex.) or "08" (hex.).
Whenthe8-bitcharactercodeoftheCGRAMiswrittentotheDDRAM, thecharacter
pattern of the CG RAM is displayed on the LCD display position corresponding to
the DD RAM address. (DD RAM data, bits 0-2 correspond to CG RAM address, bits
3-5.)
19/49
OKI [ OKI ELECTRONIC COMPONETS ]
