[SOLVED] GLCD KS0108 Dummy read. When? Once?

[atferrari]

dummy read

The datsheet of the KS0108 mentions the need of a dummy read whose results should be discarded.

My questions:

A) This dummy read is to be done:

Just the first time I read RAM data, after a reset?

Every time I want to read data from RAM?

The first time after reset and the first time after any write?

B) What materializes the second reading? In other words: just bringing the E pin high and then low again, generates the second reading?

Gracias for any help.

 

[wp100]

ks0108

Hi,

It is possible to program that glcd with 18F assembler, but its harder than the more modern units because the display uses the two ks0108 controllers, and you have to control both of them separately; also with it being parallel unit it takes a load of ports to run it compared to the modern serial /spi units.

The Dummy Read is when you use the more advanced features of controlling the data.
When the Pic outputs its data it is saved in the glcds Display RAM, and its when you want to read back this data to the Pic that you must then do the Dummy read.
This is to preload its output register and only needs to be done when you initiate a new read / address sequence.

There are no other Dummy reads /write needed that I know of

 

[Kurenai_ryu]

ks0108 dummy read

well accoding the datasheet, you need a dummy read each time you need to read the DATA RAM, (not status reg) so.. if you are reading just one position, you must read it twice... (according datasheet) if you are reading two or more bytes, make a dummy read, and then read all your bytes....

all according the datasheet i got from a simple google search...

 

[ali1011]

hi all
I write a program with codevision and for putting a pixel a should read the Glcd ram.
I cant understand what is real dummy read, but I write a function for this.
can you help me?

unsigned char r_data(void)
{
unsigned char a;
DDRC=0x00; \\Change Port C to Input
RW=1;
RS=1;

E=1;
delay_us(5);
E=0;
delay_us(5);
E=1;

delay_us(5);
E=0;
RW=0;
a = DATA_LCD;
DDRC=0xFF;
return a;
}