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HowTo: How To Build A Parallel Port Controller Box
( Hill Robertson)
Step 9 : Write Sequence
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1. (First Write) The data byte (8 bits) is set on the 8 data bits of the parallel port
2. (Second Write) The flip flop control bit is set low (0V) which is inverted. This latches the data in the flip flop and is stored (like memory) in the FF.
3. (Third Write) The flip flop control bit is set back to high (+5V) to keep the flip flop data from changing before it is sent to the box flip flops.
4. (Fourth Write) The steering data byte is set on the port.
5. (Fifth Write) The decoder control bit is set high to send out a clock (low) to the specific box flip flop.
6. (Sixth Write) The destination flip flop latches the data and turns on or off the lights via the 8 circuit boxes and holds it's state until the next instruction is sent to change it.
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