trs80m1: fix NMI handling up a bit for the Model III

We have to be really careful about this as the ROM helpful trashes AF

diff --git a/Kernel/platform-trs80m1/floppy3.s b/Kernel/platform-trs80m1/floppy3.s
index dc5b082..24a8a67 100644 (file)
--- a/Kernel/platform-trs80m1/floppy3.s
+++ b/Kernel/platform-trs80m1/floppy3.s
@@ -12,7 +12,6 @@
 ;      FIXME: precompensation
 ;              - not on single density
 ;              - track dependant for double density based on trsdos dir pos
-;      FIXME: wire up NMI and correct the masking of it we do
 ;      FIXME: fix the tiny motor/start command race. I think it's safe
 ;              but check
 ;      FIXME: backport fixes to model 4
@@ -28,6 +27,7 @@
        .globl _fd_tab
        .globl _fd_cmd
        .globl map_kernel, map_process_always
+       .globl nmi_handler
 
 FDCREG .equ    0xF0
 FDCTRK .equ    0xF1
@@ -73,11 +73,19 @@ nap:        dec     bc
 ;      fdc_active must never be set when interrupts are enabled or we may
 ;      take a motor off during an interrupt...
 ;
+;      Nasties:
+;      The model 3 executes the following code on an NMI (plus some misc
+;      jumps in the process)
+;      IN A(E4)        ; corrupting A of whatever is running
+;      BIT 5,A
+;      JP NZ, 4049     ; if not reset button user vector
+;
+;      So we can only enable the NMI in tightly controlled situations
+;
 fd_nmi_handler:
-       push    af
        ld      a, (fdc_active)
        or      a
-       jr      z, boring_nmi
+       jp      z, nmi_handler  ; Dead
        xor     a
        out     (FDCINT), a
        push    bc
@@ -89,12 +97,6 @@ fd_nmi_handler:
        jp      fdio_nmiout     ; and jump
 
 ;
-;      FIXME: check for motor off here
-;
-boring_nmi:
-       pop     af
-       retn
-;
 ;      Wait for the drive controller to become ready
 ;      Preserve HL, DE
 ;
@@ -208,9 +210,10 @@ patchfor256:
 ;
        nop                             ; 44
 fdxferdone:
-       xor     a                       ; 48
-       ld      (fdc_active), a         ; 55
-       ei                              ; 59
+       xor     a                       ;
+       ld      (fdc_active), a         ; 
+       out     (FDCINT),a              ; 
+       ei                              ;
        in      a, (FDCREG)
        and     #0x19                   ; Error bits + busy
        bit     0, a                    ; Wait for busy to drop, return in a
@@ -280,10 +283,12 @@ fdio_waitlock:
        jr      z, fdio_waitlock
        out     (c), b
        ld      a, d
+       ld      b, #1
 fdio_outbyte:
        out     (FDCCTRL), a            ; stalls
        outi
-       jr      fdio_outbyte
+       jr      nz,fdio_outbyte
+       
 fdio_nmiout:
 ;
 ;      Now tidy up