
DISPLAY PORT
DISPLAY TYPES
| Manu fact. | Model | Type | 
| Optrex | DMC 40457 | LCD 4 x 40 | 
| Optrex | DMC 40202 | LCD 2 x 40 | 
| IEEE | VF 4 x 20 | |
| Optrex | DMF 682N | LCD 160W x 128D | 
DISPLAY CONNECTOR PIN OUT
The displa y port uses an 82C5 5 for data and contr ol. The table below lists a pin number and its intended function. A display may not use all lines even though they are available.
| J4 | 8255 | Function | 
| Pin | Port/line | 
 | 
| 1 | 
 | Logic + 5V | 
| 2 | 
 | Digital ground | 
| 3 | A/4 | D4 | 
| 4 | 
 | Contrast voltage | 
| 5 | A/6 | D6 | 
| 6 | A/5 | D5 | 
| 7 | B/4 | Reset (from invertor) | 
| 8 | B/3 | Write | 
| 9 | B/2 | Read | 
| 10 | A/7 | D7 | 
| 11 | A/1 | D1 | 
| 12 | A/0 | D0 | 
| 13 | A/3 | D3 | 
| 14 | A/2 | D2 | 
| 15 | B/7 | CS (from invertor) | 
| 16 | B/6 | Com mand/ data | 
| 17 | B/5 | Halt | 
| 18 | 
 | Contrast adjust | 
| 19 | 
 | Alternate power | 
| 20 | 
 | Power gr ound | 
J4 is available for additional I/O if a display is not used. Port A is configured as an input or output. P ort B must be configur ed as an outpu t if a 17 key or larger keypad is used. Use the L INE B comm and to acces s this part.
I/O bank is 4.
Pins 18, 19, and 20 are for the LCD 
SECTION 8
COMMANDS
The following 
| Comm and | Function | 
| CLEAR DISPLAY | Clears entire display | 
| CLEAR DISPLAY LINE Clears curr ent line | |
| CONFIG DISPLAY | Specifies display type to | 
| 
 | use | 
| DISPLAY | Prints the string at the | 
| 
 | row and collum specified | 
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