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 +1,42 @@
+; A write protected disk.
+;
+; The bar is in the device, not in the filesystem. A flag in a superblock can be got
+; around by writing blocks directly; this cannot be got around at all. It is the tab on
+; the side of a floppy rather than a note asking politely.
+;
+; A disk is read only if it was attached that way, or if the host will not let its image
+; be written. The machine cannot tell the two apart and does not need to.
+;
+; Status bit 2 says the disk is protected. Unlike the busy and error bits it describes the
+; medium rather than the last operation, so it reads true before anything has been asked
+; of the disk at all.
+;
+; Correct output is:
+;   04                protected, before anything has been attempted
+;   04                a read is allowed and does not disturb the bit
+;   06                a write is barred: protected, and the operation failed
+
+#Include print.asm
+
+#Program
+
+start:
+  INA 0x23
+  CALL printByteHex
+  CALL lineFeed
+
+  RSTA
+  OUTA 0x20
+  OUTA 0x21             ; Block 0.
+  INIA 0x01
+  OUTA 0x22             ; Read. Reading a protected disk is ordinary.
+  INA 0x23
+  CALL printByteHex
+  CALL lineFeed
+
+  INIA 0x02
+  OUTA 0x22             ; Write. Barred by the device.
+  INA 0x23
+  CALL printByteHex
+  CALL lineFeed
+  HALT