dragon: Fix up comments in setup.s

Signed-off-by: Tormod Volden <debian.tormod@gmail.com>

diff --git a/Kernel/platform-dragon/setup.s b/Kernel/platform-dragon/setup.s
index b5d9211..7b99588 100644 (file)
--- a/Kernel/platform-dragon/setup.s
+++ b/Kernel/platform-dragon/setup.s
@@ -16,9 +16,8 @@ bootme:
        sta 0xff22              ; after this we are in the other rom
 
 main:
-       ; Optimise all this to use the direct page register as 0xffxx
        orcc #0x10
-       ; Memory 64K dynamic (I guess...)
+       ; Optimise all this to use the direct page register as 0xffxx
        lda #0xFF
        tfr a,dp        ; So we can short form all our I/O operations
 
@@ -28,32 +27,34 @@ main:
 ;      Start by resetting the SAM registers in case we are a soft reset
 ;
        lda #0x10
-       ldx #0xffc0     ; SAM
+       ldx #0xffc0     ; SAM registers 0xffc0-0xffdf
 samwipe:
-       sta ,x++        ; X is now 0xffd0
+       sta ,x++        ;
        deca
        bne samwipe
 
        sta 0xffcf      ;
        sta 0xffd1      ; Display at 0x6000
-       sta 0xffd3      ; In the upper bank
+       sta 0xffd3      ; In the upper bank (= 0xe000)
        ;FIXME - DD or DB needed to get it right
+       ; Memory 64K dynamic (I guess...)
        sta 0xffdd      ; 64K dynamic RAM
        sta 0xffd5      ; Use RAM bank 1 at 0x0000 (providing ffde is clear)
 
+;      Configure PIAs
        ; PIA0 A is all input
        ; PIA0 B is all output
        ; PIA1 A is mixed, both the same (input 0 only)
 
        lda #0x04
-       sta 0xff23      ; Set 0xFF22 to be data
+       sta 0xff23      ; Set 0xFF22 to access data register
        sta 0xff22      ; Ensure we don't glitch the ROM select bit
 
        clr 0xff01      ; Control to zero - direction accessible
        clr 0xff03
        clr 0xff21      ; Do both PIA devices
        clr 0xff23
-       clr 0xff00
+       clr 0xff00      ; PIA0 A all input
        lda #0xff
        sta 0xff02      ; Set PIA0 B as output (keyboard matrix)
        lda #0x34