Pixel display
This code from block 848 is loaded into green node 713. This is one of many blocks that generate video D/A output. It displays text pixels.
go
An infinite loop:
- Waits for a character
- If negative, goes to sol
- Sets black into a
- For 6 pixels (5 plus blank)
- Waits 12 unexts
- Shifts left and calls pix
pix
Timing must be the same for bright and dark. Bright is on the stack and dark in a.
- If the stack is negative, the pixel is 1 (bright). The intensity is set from under the stack
- Otherwise the pixel is 0 and dark is set from a
sol
Wait for Start of Line
- Save and restore a
- Write any word to up
- Fall into go
The up port is read to get the A/D counter. It is never really written, so its write decode is borrowed to test pin 71. And that write is delayed until the pin goes high. The write goes nowhere, but the stack is popped.
The framing node puts a short pulse on pin 71; sol will waken on the rising edge.
init
Three intensities are listed; medium is chosen.
I'm thinking execution should start at sol not go