zx128: first cut at write logic

Not yet wired up to checksum, and some of the delay loops need tuning so we
don't scribble too early.

diff --git a/Kernel/platform-zx128/microdrive.s b/Kernel/platform-zx128/microdrive.s
index 4b589c1..5bb5b10 100644 (file)
--- a/Kernel/platform-zx128/microdrive.s
+++ b/Kernel/platform-zx128/microdrive.s
@@ -33,6 +33,7 @@
                .globl _mdv_hdr_buf
                .globl _mdv_len
                .globl _mdv_page
+               .globl _mdv_csum
 
                .globl map_process_save
                .globl map_kernel_restore
@@ -155,7 +156,6 @@ mdv_hdr_only:
                or a
                ret
 
-
 ;
 ;      Load the next header, well probably header - you might get the
 ;      start of a data chunk, in which case try again
@@ -261,6 +261,55 @@ failblk:
                ret
 
 ;
+;      IRQ had must be off here...
+;
+mdv_put_blk:   ld a, #0xE6
+               out (0xEF), a                   ; Write mode
+               ld de, #0x0168                  ; Wait for record
+               call nap                        ; May need to be a shade
+                                               ; longer. Compare timings
+                                               ; with Sinclair ROM
+               ld hl, #_mdv_hdr_buf            ; Header to write first
+               ld a, (_mdv_csum)
+               ld e, a
+               ld a, #0x03                     ; Magneta border
+               out (0xFE), a
+               ld a, #0xE2
+               out (0xEF), a                   ; Ready...
+               nop                             ; FIXME: use a shorter
+               nop                             ; way to wait 24 clocks
+               nop
+               nop
+               nop
+               nop
+               ld c, #0xE7                     ; Data port
+               ld b, #0x1E                     ; Header
+               otir                            ; Header bytes out
+               ld hl, (_mdv_buf)
+               otir                            ; First 256 data
+               otir                            ; Last 256 data
+               out (c), e                      ; and the checksum
+               ld a, #0xE6
+               out (0xEF), a
+               xor a
+               out (0xFE), a                   ; Back in black
+               ld a, #0xEE
+               out (0xEF), a                   ; Writing off
+               xor a
+               ret
+
+;
+;      Write a sector from memory
+;
+mdv_store:     in a, (0xef)
+               and #1
+               jr nz, mdv_put_wp               ; write protected
+               call mdv_find_hdr               ; find the header we want
+               call z, mdv_put_blk             ; write the block after it
+               ret                             ; done
+mdv_put_wp:    ld a, #4                        ; write protected - fail
+               ret
+;
 ;      Load a sector into memory.
 ;
 mdv_fetch:     call mdv_find_hdr               ; nz = not found
@@ -364,6 +413,7 @@ _mdv_bread:
                push af
                call nz, map_process_save
                call mdv_fetch
+mdv_bout:
                jr nz, poprete
                xor a
 poprete:
@@ -375,7 +425,10 @@ poprete:
                ret
 
 _mdv_bwrite:
-               ld hl, #0xffff          ; not done yet
-               ret
-
+               ld a, (_mdv_page)
+               or a
+               push af
+               call nz, map_process_save
+               call mdv_store
+               jr mdv_bout