From a016fb0981918bef8fd36cff09738a8521149eda Mon Sep 17 00:00:00 2001
From: Nero <41307858+nero@users.noreply.github.com>
Date: Thu, 24 Oct 2019 23:11:19 +0000
Subject: [PATCH] PoC CBIOS

---
 bios/8086.asm | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 bios/8086.asm

diff --git a/bios/8086.asm b/bios/8086.asm
new file mode 100644
index 0000000..c939e49
--- /dev/null
+++ b/bios/8086.asm
@@ -0,0 +1,142 @@
+ORG (RAM-0x600)
+CPU 8086
+
+DISKCX: EQU 0x40
+DISKDL: EQU 0x42
+DISKDH: EQU 0x43
+DISKBX: EQU 0x44
+
+JMP NEAR BOOT
+JMP NEAR WBOOT
+JMP NEAR CONST
+JMP NEAR CONIN
+JMP NEAR CONOUT
+JMP NEAR LIST
+JMP NEAR PUNCH
+JMP NEAR READER
+JMP NEAR HOME
+JMP NEAR SELDSK
+JMP NEAR SETTRK
+JMP NEAR SETSEC
+JMP NEAR SETDMA
+JMP NEAR READ
+JMP NEAR WRITE
+JMP NEAR LISTST
+JMP NEAR SECTRAN
+
+BOOT:
+  STC
+  RET
+
+WBOOT:
+  STC
+  RET
+
+; CHAR I/O
+CONST:
+  MOV AH, 1
+  INT 0x16
+  JZ .END
+  MOV AL, 0xFF
+  RET
+.END:
+  XOR AL, AL
+  RET
+
+CONIN:
+  XOR AX, AX
+  INT 0x16
+  TEST AL, AL
+  JZ CONIN
+  RET
+
+CONOUT:
+  PUSH AX
+  PUSH BX
+  MOV AH, 0x0E
+  MOV AL, DL
+  XOR BX, BX
+  INT 0x10
+  POP BX
+  POP AX
+  RET
+
+LIST:
+  PUSH DX
+  XOR AH, AH
+  MOV AL, DL
+  INT 0x17
+  POP DX
+  RET
+
+LISTST:
+  STC
+  RET
+
+PUNCH:
+  STC
+  RET
+
+READER:
+  STC
+  RET
+
+; DISK I/O
+HOME:
+  RET
+
+SELDSK:
+  MOV BYTE [DISKDL], CL
+  XOR BX, BX
+  RET
+
+SETTRK:
+  PUSH CX
+  PUSH DX
+
+  MOV DX, CX
+  ; CH for headnum, CL for SAL
+  MOV CX, 0x0006
+
+  ; Take off LSB as head number
+  XOR CH, CH
+  RCR DX, 1
+  RCL CH, 1
+  MOV BYTE [DISKDH], CH
+
+  ; DX is sector number now
+  ; Shift into format for int13
+  ; DX ------9876543210
+  SAL DX, CL
+  ; DX 9876543210------
+  ROL DX, 1
+  ROL DX, 1
+  ; DX 76543210------98
+  SAL DL, CL
+  ; DX 7654321098------
+  AND WORD [DISKCX], 0x003F
+  OR WORD [DISKCX], DX
+
+  POP DX
+  POP CX
+  RET
+
+SETSEC:
+  STC
+  RET
+
+SETDMA:
+  MOV WORD [DISKBX], CX
+  RET
+
+READ:
+  STC
+  RET
+
+WRITE:
+  STC
+  RET
+
+SECTRAN:
+  STC
+  RET