Memory controller implemented.

2026-08-15 20:43:53 -04:00
parent c4b2c27a2d
commit 04dfcd707b
32 changed files with 1842 additions and 21 deletions
@@ -0,0 +1,210 @@
+; Blits and fills.
+;
+; A blit moves a run of bytes between any two banks, including from one place in a bank
+; to another. A fill writes one byte across a run. Both are instantaneous: waiting
+; belongs to a peripheral that has something to wait for, not to the moving of bytes.
+;
+; Everything a transfer will touch is checked before any of it moves, so a transfer that
+; would run out of bank refuses outright rather than stopping halfway and leaving memory
+; in a state nobody asked for. The last case here proves that: the blit is refused, and
+; the bytes it would have written are still what they were.
+;
+; Correct output is:
+;   blitted           copied from one place in Data Memory to another
+;   ....              filled with a byte of our choosing
+;   DE AD             blitted from Data Memory into Program Memory
+;   untouched         a refused blit moved nothing at all
+;   ABABCDEFGH        an overlapping blit slid the bytes rather than repeating one
+
+#Include print.asm
+
+#Program
+
+start:
+  ; ---- A blit inside Data Memory, which is what a memcpy is here. ----
+  SETD.0 Message
+  CALL aimSource
+  SETD.0 Landing
+  CALL aimDest
+  INIA 0d8
+  CALL setLength        ; "blitted" and its terminator.
+  INIA 0x01
+  OUTA 0xE8             ; Blit.
+
+  SETD.0 Landing
+  CALL printString
+  CALL lineFeed
+
+  ; ---- A fill, with a byte of our choosing rather than only zero. ----
+  SETD.0 Landing
+  CALL aimDest
+  INIA 0x2E             ; '.', into SourceLow, which is where a fill takes its byte.
+  OUTA 0xE2
+  INIA 0d4
+  CALL setLength
+  INIA 0x02
+  OUTA 0xE8             ; Fill.
+
+  ; Terminate it so printString knows where to stop.
+  SETD.0 Landing
+  DPUP.0 0d04
+  RSTA
+  STA.0
+  SETD.0 Landing
+  CALL printString
+  CALL lineFeed
+
+  ; ---- Data Memory into Program Memory. This is what a loader does. ----
+  SETD.0 Code
+  CALL aimSource
+  SETD.0 Target
+  CALL aimDestProgram
+  INIA 0d2
+  CALL setLength
+  INIA 0x01
+  OUTA 0xE8             ; Blit.
+
+  ; Read it back out of Program Memory to prove it landed.
+  SETD.0 Target
+  CALL aimSourceProgram
+  CALL readAndPrint
+  CALL readAndPrint
+  CALL lineFeed
+
+  ; ---- A blit that would run past the end of bank 2. ----
+  ; Bank 2 is 2048 bytes. Starting at 2040 and asking for 16 does not fit, so the whole
+  ; thing is refused and Landing keeps what it already had.
+  SETD.0 Untouched
+  CALL aimSource
+  SETD.0 Landing
+  CALL aimDest
+  INIA 0d10
+  CALL setLength
+  INIA 0x01
+  OUTA 0xE8             ; This one works, so Landing says "untouched".
+
+  INIA 0d2
+  OUTA 0xE0             ; SourceBank = 2, the bank table.
+  INIA 0x07
+  OUTA 0xE1
+  INIA 0xF8
+  OUTA 0xE2             ; 0x07F8, eight bytes from the end.
+  SETD.0 Landing
+  CALL aimDest
+  INIA 0d16
+  CALL setLength
+  INIA 0x01
+  OUTA 0xE8             ; Refused: it would read past the end of bank 2.
+
+  SETD.0 Landing
+  CALL printString
+  CALL lineFeed
+
+  ; ---- A blit whose source and destination overlap. ----
+  ; Sliding a run of bytes along inside its own bank is an ordinary thing to want, so it
+  ; works rather than quietly repeating the first byte the way a naive forward copy does.
+  SETD.0 Slide
+  CALL aimSource
+  SETD.0 Slide
+  DPUP.0 0d02
+  CALL aimDest
+  INIA 0d8
+  CALL setLength
+  INIA 0x01
+  OUTA 0xE8
+
+  SETD.0 Slide
+  CALL printString
+  CALL lineFeed
+  HALT
+
+; ---- Helpers. DP0 holds the address to aim at. ----
+
+aimSource:
+  INIA 0d1              ; Bank 1, Data Memory.
+  OUTA 0xE0
+  BRI aimSourceAddress
+aimSourceProgram:
+  RSTA                  ; Bank 0, Program Memory.
+  OUTA 0xE0
+aimSourceAddress:
+  PSHD.0
+  POPA
+  POPB
+  OUTB 0xE1
+  OUTA 0xE2
+  RET
+
+aimDest:
+  INIA 0d1              ; Bank 1, Data Memory.
+  OUTA 0xE3
+  BRI aimDestAddress
+aimDestProgram:
+  RSTA                  ; Bank 0, Program Memory.
+  OUTA 0xE3
+aimDestAddress:
+  PSHD.0
+  POPA
+  POPB
+  OUTB 0xE4
+  OUTA 0xE5
+  RET
+
+; A is the length, which is never more than a byte in this program.
+setLength:
+  PSHA
+  RSTA
+  OUTA 0xE6
+  POPA
+  OUTA 0xE7
+  RET
+
+readAndPrint:
+  INA 0xE9
+  CALL printByteHex
+  CALL blankSpace
+  RET
+
+; The refused blit is caught so the program can carry on and show that nothing moved.
+; The command write is two bytes, an opcode and a port, so stepping by two gets past it.
+refusedHandler:
+  MVSD.0
+  DPUP.0 0d14
+  LDA.0
+  CCF
+  INIB 0d2
+  ADD
+  MVQA
+  STA.0
+  BRC refusedCarried
+  RETI
+refusedCarried:
+  DPDN.0 0d01
+  LDA.0
+  INCA
+  STA.0
+  RETI
+
+; Never executed, only written over.
+Target:
+  0x00 0x00
+
+#Data
+
+Message:
+"blitted"
+Untouched:
+"untouched"
+Code:
+  0xDE 0xAD
+
+Landing:
+  #Reserve 0d16
+
+Slide:
+"ABCDEFGH"
+  #Reserve 0d4
+
+#Vectors
+
+  BankFault  refusedHandler