trs80: fix bank94 code

With these fixes this code now correctly sizes and manages extended banking

diff --git a/Kernel/platform-trs80/trs80-bank94.s b/Kernel/platform-trs80/trs80-bank94.s
index 29f93e8..7fb10a3 100644 (file)
--- a/Kernel/platform-trs80/trs80-bank94.s
+++ b/Kernel/platform-trs80/trs80-bank94.s
@@ -71,7 +71,7 @@ _modout:    .db 0x50  ; 80 column, sound enabled, altchars off,
 detect94:
             in a,(0x94)
             cp #0xFF
-             jr z, nobank94
+             jr z, bank94_absent
 ;
 ;      Seems we have banking extensions present
 ;
@@ -80,6 +80,8 @@ detect94:
 ;      For each bank check the byte selected is A5 and write the bank into
 ;      it. When we see a bank not reporting A5 we have found the wrap.
 ;
+           ld a, #0x63         ; map extended memory into low 32K
+           out (0x84),a
            ld a, #0xA5
            ld bc, #0x1f94
            ld hl, #0x80        ; pick somewhere which won't hit us!
@@ -97,6 +99,8 @@ scanall:    inc b
            ld (hl), b
            jr scanall
 scandone:
+           ld a,(_opreg)       ; restore mapping of kernel
+           out (0x84),a
            ld a, b
            ld (_nbanks), a
            xor a
@@ -109,7 +113,7 @@ scandone:
            ld l, a     ; Report size in HL
            ld h, b
            ret
-nobank94:
+bank94_absent:
            xor a
            ld h, a
            ld l, #128          ; We ought to check/abort on a 64K box ?