Memory controller implemented.

Programs/testPrograms/refusalTest.asm

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+; Tests a device refusing what it was asked to do.
+;
+; Interrupting is a device asking for attention later. Refusing is a device saying no to
+; the instruction happening now, so it has to stop the machine where it stands instead of
+; letting execution carry on past the mistake.
+;
+; The device on port 0x11 refuses everything, in both directions, so that this path can
+; be exercised without the memory controller. A refusal names a software vector, so the
+; handler knows what happened from the entry it arrived through.
+;
+; The handler steps the saved address past the instruction that was refused, the same way
+; the fault handler steps past a byte that would not decode. Without that a bare RETI
+; would meet the same refused instruction again forever.
+;
+; Correct output is:
+;   caught      the handler caught a refused write
+;   caught      and a refused read
+;   done
+
+#Include print.asm
+
+#Program
+
+start:
+  INIA 0d1
+  OUTA 0x11         ; Refused. The handler runs and steps us past this.
+
+  INA 0x11          ; Refused as well, and reads are caught the same way.
+
+  SETD.0 Done
+  CALL printString
+  CALL lineFeed
+  HALT
+
+; A refusal arrives with a full frame, so the handler may use whatever it likes.
+refusalHandler:
+  CALL reportRefusal
+
+  ; Step the saved address past the instruction that was refused. Both OUT and IN are
+  ; two bytes, an opcode and a port, so two is what it takes.
+  MVSD.0
+  DPUP.0 0d14
+  LDA.0
+  CCF
+  INIB 0d2
+  ADD
+  MVQA
+  STA.0
+  BRC carried
+  RETI
+
+carried:
+  DPDN.0 0d01
+  LDA.0
+  INCA
+  STA.0
+  RETI
+
+reportRefusal:
+  SETD.0 Caught
+  CALL printString
+  CALL lineFeed
+  RET
+
+#Data
+
+Caught:
+"caught"
+Done:
+"done"
+
+#Vectors
+
+  GuardViolation  refusalHandler