Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

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

Status
Not open for further replies.

atferrari

Full Member level 4
Joined
Jun 29, 2004
Messages
237
Helped
7
Reputation
14
Reaction score
3
Trophy points
1,298
Location
Buenos Aires - Argentina
Activity points
1,996
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

Advanced Member level 5
Joined
May 15, 2009
Messages
3,056
Helped
883
Reputation
1,781
Reaction score
736
Trophy points
113
Location
Prime Meridian
Activity points
0
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

Advanced Member level 2
Joined
Jun 10, 2006
Messages
671
Helped
159
Reputation
316
Reaction score
99
Trophy points
1,308
Location
Bolivia
Activity points
5,913
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

Newbie level 1
Joined
Sep 25, 2009
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,284
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?
Code:
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;
}
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top