Last Updated or created 2024-08-22
PROCESSOR FUNCTION CODES (FC0, FC1, FC2)
These function code outputs indicate the mode (user or supervisor) and the address space type currently being accessed.
The following table shows the
meaning of these three bits.
FC2 FC1 FC0 Meaning
0 0 0 Not used
0 0 1 User data
0 1 0 User program
0 1 1 Not used
1 0 0 Not used
1 0 1 Supervisor data
1 1 0 Supervisor program
1 1 1 Interrupt Acknowledge
These outputs can therefore inform external circuitry what is happening
inside the 68000. They could, for example, be used to switch in differentbanks of memory.Using a small 8266 with a display, I wanted to see if it’s useful to monitor this information.
So using a trick with the uln2804/uln2803 as level convertor (don’t connect the VCC, and the output will drop to a level that is around the 3.3v.
(I was out of bi-directional level convertors)
Latch demo
I’ve been using latches in the past, but I wanted to show how it works using a little demo setup.
Below movie is for the Bus Controller I posted recently.
