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Circuit Description

This applet demonstrates a microprogrammed sequencer. The output of the microprogram counter (uPC) addresses one address of the microprogram ROM, which in turn generates the next microprogram address and a set of data outputs.

As the X output of the microprogram ROM is directly connected to the uPC data input, this circuit can only generate a single and fixed sequence of memory addresses. For example, the default memory data uses the following X values,

addr  X
00    01
01    02
02    03
03    04
04    05
05    00

To watch and change the microprogram use the edit command (popup->edit) on the microprogram ROM component to open the memory editor window. In the memory editor, use mouse double-clicks to toggle individual bits or enter the values numerically (0,1,...F).