Differences

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--- builderpages:plasmo:zzrcc:cpldrom [2020/12/16 08:14]
plasmo
+++ builderpages:plasmo:zzrcc:cpldrom [2020/12/18 08:43] (current)
plasmo
@@ Line 6: / Line 6: @@
 <code>
-;12/5/20
+;12/18/20
 ;32-byte ROM inside CPLD
-;check for CF disk not busy, then read the master boot record to 0xB000
+;check for CF disk not busy, then read the master boot record to 0xB080
-;  execute the program starting from 0xB000
+;  execute the program starting from 0xB080
 CFdata       equ 010h        ;CF data register
 CFerr        equ 011h        ;CF error reg
@@ Line 20: / Line 20: @@
     org 0
-    nop
+    ld c,8        ;point to I/O page register
-    nop
+    ld l,0        ;CF is in page 0
-    nop
+    db 0edh,6eh    ;op code for LDCTL (C),HL
-    ld hl,0b000h    ;bootstrap code starts from 0xb000
 ; check for disk not busy
 readbsy:
     in a,(CFstat)    ; read CF status
-    and 80h        ; mask off all except busy bit
+    rla
-    jr nz,readbsy
+    jr c,readbsy
-;reg A is already 0
+; do not need to set up sector/track and sector count because
-    ld b,a        ;make reg B zero
+;  they are set by default after reset
-;; do not need to set up sector/track and sector count because
-;;   they are set by default after reset
 ;    out (CF1623),a    ; track 0
 ;    out (CF815),a
@@ Line 47: / Line 45: @@
     jr z,chkdrq
-    inir        ;z80 read 256 bytes
+    ld c,CFdata
-    jp 0b000h         ;execute loaded program
+    ld hl,0b080h      ;copy program to 0xB080
+    ld b,l
-    end
+    inir        ;z80 read 128 bytes
+    jp 0b080h
 </code>