LCD programing

rfjhh · Joined: 31 Mar 2011 Posts: 51 Location: Mexico

Why in the LCD.c file, if I want to write (lcd_putc), a read routine is performed before the writing routine?
What is being checked before the execution of data writing? There is some documentation about it???

newguy · Joined: 24 Jun 2004 Posts: 1907

Before you attempt to access the LCD you first need to "ask" it if it is busy; it will hold its data bit 7 high if it is busy. All the driver is doing is checking this busy flag and waiting until it clears, if it is set, before proceeding.

You can omit the read if you respect the delays that you'll need to give the LCD between accesses in order to allow it to complete one task before giving it another.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

The flex lcd driver in the code library forum has the option of not using
the R/W line and therefore it doesn't poll the busy bit. It uses delays
as newguy said.

rfjhh · Joined: 31 Mar 2011 Posts: 51 Location: Mexico

Thanks.
Another question: What's lcdlat, where is it???

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Use the forum's search page to find the threads that have lcdlat in them.
Here is the link to the search page:
http://www.ccsinfo.com/forum/search.php

temtronic · Posted: Wed Feb 01, 2017 10:06 am

lcdlat could refer to the 'latch' or output port of a PIC. Newer PICs have them.
My version of LCD.C and FlexLCD.c do not have 'lcdlat' though.

Jay

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Come on Jay, the search engine shows it to be in the Code Library.
It's a #byte statement for the LCD's data port.

temtronic · Posted: Wed Feb 01, 2017 11:29 am

hmm.. I just checked again and neither my copies of lcd.c and flex_lcd.c have 'lcdlat' in them, according to edit>find......

now I'm thinking I may have old versions and they've been 'updated' over the past few years ?

Jay

rfjhh · Joined: 31 Mar 2011 Posts: 51 Location: Mexico

Guys

I've find where, in LCD.c, the lcdlat definition is made:

#if defined(__PCB__)
LCD_PIN_MAP lcd, lcdlat;
#byte lcd = LCD_DATA_PORT
#byte lcdlat = LCD_DATA_PORT
#elif defined(__PCM__)
LCD_PIN_MAP lcd, lcdlat, lcdtris;
#byte lcd = LCD_DATA_PORT
#byte lcdlat = LCD_DATA_PORT
#byte lcdtris = LCD_DATA_PORT+0x80
#elif defined(__PCH__)
LCD_PIN_MAP lcd, lcdlat, lcdtris;
#byte lcd = LCD_DATA_PORT
#byte lcdlat = LCD_DATA_PORT+9
#byte lcdtris = LCD_DATA_PORT+0x12
#elif defined(__PCD__)
LCD_PIN_MAP lcd, lcdlat, lcdtris;
#word lcd = LCD_DATA_PORT
#word lcdlat = LCD_DATA_PORT+2
#word lcdtris = LCD_DATA_PORT-0x02
#endif
#endif //LCD_DATA4 not defined

Thanks