Block device peripheral and SBFS file system implemented.

2026-08-16 14:03:29 -04:00
parent 04dfcd707b
commit eff6902bcf
36 changed files with 3251 additions and 31 deletions
@@ -0,0 +1,184 @@
+; Loads a program off a disk and runs it.
+;
+; Everything this needs already existed: the filesystem reads the file, the controller
+; writes Program Memory, and BRD jumps to an address worked out at run time. The only new
+; part is the sixteen bytes on the front of a loadable program that say where it goes.
+;
+; Nothing relocates anything. The program is put exactly where its header asks, and that
+; has to be where it was assembled for, or every branch inside it points somewhere wrong.
+; This loader therefore keeps out of the way: its own code and data sit above the
+; addresses the loaded program claims, which is an arrangement rather than a mechanism.
+;
+; Correct output is:
+;   loader
+;   loaded off a disk, with a string and a loop of its own
+
+#Include print.asm
+#Include sbfs.asm
+
+#Program
+
+; print.asm branches here at the top of the Program Segment, so this is where the machine
+; arrives whether or not the Boot Vector is obeyed. Naming it in the Vector Segment as
+; well says plainly where the program begins.
+start:
+  SETD.0 LoaderName
+  CALL printString
+  CALL lineFeed
+
+  CALL sbfsMount
+  BNQ loaderNoDisk
+
+  SETD.0 ProgramName
+  CALL sbfsFind
+  BNQ loaderMissing
+
+  SETD.1 Staging
+  CALL sbfsRead
+  BNQ loaderUnreadable
+
+  ; "SBEX", or it is not a program at all. Loading a text file would otherwise put
+  ; nonsense into Program Memory and jump into it.
+  SETD.0 Staging
+  SETD.2 ExecMagic
+  INIA 0d4
+  SETD.1 LoaderCount
+  STA.1
+loaderMagicLoop:
+  LDA.0
+  LDB.2
+  XOR
+  BNQ loaderNotProgram
+  INCD.0
+  INCD.2
+  LDA.1
+  DECA
+  STA.1
+  BNA loaderMagicLoop
+
+  SETD.0 Staging
+  DPUP.0 0d04
+  LDA.0
+  INIB 0d1
+  XOR
+  BNQ loaderWrongVersion
+
+  ; The code first. Source is the bytes just past the header; destination is wherever the
+  ; header says the code lives.
+  INIA 0d1
+  OUTA 0xE0             ; SourceBank: Data Memory, where the file was read to.
+  SETD.0 Staging
+  DPUP.0 0d16
+  PSHD.0
+  POPA
+  POPB
+  OUTB 0xE1
+  OUTA 0xE2
+
+  RSTA
+  OUTA 0xE3             ; DestBank: Program Memory.
+  ; Where the code goes. Read and written out a byte at a time rather than through a
+  ; subroutine, because a subroutine could not hand the two bytes back: CALL preserves
+  ; A and B along with the first three Data Pointers, so anything a routine puts in them
+  ; is undone by its own return.
+  SETD.0 Staging
+  DPUP.0 0d06
+  LDA.0
+  OUTA 0xE4
+  INCD.0
+  LDA.0
+  OUTA 0xE5
+
+  ; How much of it there is.
+  SETD.0 Staging
+  DPUP.0 0d10
+  LDA.0
+  OUTA 0xE6
+  INCD.0
+  LDA.0
+  OUTA 0xE7
+
+  INIA 0x01
+  OUTA 0xE8             ; Blit.
+
+  ; Then the data. A blit leaves its addresses past whatever it touched, so the source is
+  ; already sitting on the first byte of the data and only the destination changes.
+  INIA 0d1
+  OUTA 0xE3             ; DestBank: Data Memory.
+  SETD.0 Staging
+  DPUP.0 0d12
+  LDA.0
+  OUTA 0xE4
+  INCD.0
+  LDA.0
+  OUTA 0xE5
+
+  SETD.0 Staging
+  DPUP.0 0d14
+  LDA.0
+  OUTA 0xE6
+  INCD.0
+  LDA.0
+  OUTA 0xE7
+
+  INIA 0x01
+  OUTA 0xE8             ; Blit.
+
+  ; And go. The entry address is a number until BRD makes it a place. DP3 is built from
+  ; the two bytes by hand, since it is the pointer nothing puts back.
+  SETD.0 Staging
+  DPUP.0 0d08
+  LDA.0
+  INCD.0
+  LDB.0
+  PSHA
+  PSHB
+  POPD.3
+  BRD.3
+
+loaderNoDisk:
+  SETD.0 NoDisk
+  BRI loaderComplain
+loaderMissing:
+  SETD.0 NotThere
+  BRI loaderComplain
+loaderUnreadable:
+  SETD.0 Unreadable
+  BRI loaderComplain
+loaderNotProgram:
+  SETD.0 NotProgram
+  BRI loaderComplain
+loaderWrongVersion:
+  SETD.0 WrongVersion
+loaderComplain:
+  CALL printString
+  CALL lineFeed
+  HALT
+
+#Data
+
+ExecMagic:
+"SBEX"
+LoaderName:
+"loader"
+ProgramName:
+"hello.sbx"
+NoDisk:
+"no disk"
+NotThere:
+"no such program"
+Unreadable:
+"could not read it"
+NotProgram:
+"not a program"
+WrongVersion:
+"a version I do not know"
+LoaderCount:
+  0x00
+
+Staging:
+  #Reserve 0d512
+
+#Vectors
+
+  Boot  start