20 x 8 Video Generator
This is a 20 character by 8 line video display. The display is limited to upper case characters, numbers, and a few punctuation marks due to space constraints in the PIC. Unlike the similar video unit, this device uses 2 PIC's - one to interface to the network and one to generate the video. This eliminates the display blanking during the network communications when using the previous design.
The network feeds the PIC12F629 on GP4. Here the network data is analyzed and only data for this specific unit is passed on the PIC16F819. To eliminate blanking of the display as the data is passed from one micro to the other, data is passed across only during the Vertical Blanking Interval. To help make this communication reliable, both PIC's run on the same 20Mhz xtal.
The PIC16F819 was taken from the previous design because it has an SPI serial port. This provides the shift register function to get data out fast enough for 20 character lines.
This unit is designated M1 on the network. Here are the available commands.
/M1Z - Clear the display.
/M1Tn XXXXXX - put characters XXXXXX on the screen at location 'n'. The location of the first line is 0, the second line is 20, etc.
Here are the files used for this device.