page 64,132  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE 1-1 Comment @ This is a patch to the ROM BIOS keyboard routine. When the patch is loaded, the Alt, Ctrl, Left Shift and Right Shift keys toggle between their shifted and unshifted states. There are two main entry points. 1. 'Keyloc' sets up the keyboard interupt vector to point to the patch instead of the normal BIOS routine. After Keyloc executes, it leaves the new interupt handler resident in memory. 2. 'Ikeyloc' is the new keyboard interupt handler. The first section is a duplication of the ROM BIOS routine until a point where tests for the input of a Alt, Ctrl, Left Shift or Right Shift key can be made. If it is one of those keys, the appropriate bits in the keyboard flag byte are twiddled. John Black 5225 Pooks Hill Rd. #1715 N. Bethesda MD. 20814 @ = 0060 port_b equ 60h ; 8255 port a addr = 0040 timer equ 40h = 0060 kb_data equ 60h ; keyboard scan code port = 0061 kb_ctl equ 61h ; control bits for keyboard sense data 0000 abso segment at 0 0024 org 24h 0024 kb_vector label dword 0024 abso ends 0000 bioscode segment at 0F000h ; ...locations in ROM BIOS used to return from interupt E9AF org 0E9AFh E9AF K16 label far ; resume code if not shift EC24 org 0EC24h EC24 K62 label far EA23 org 0EA23h EA23 K23 label far ; break for shift key EA5E org 0EA5Eh EA5E K26 label far ; return from interupt EA5E bioscode ends 0000 biosdata segment at 40h 0017 org 17h 0017 kb_flag label byte ; ...bit definitions for kb_flag = 0080 ins_state equ 80h ; insert state is active = 0040 caps_state equ 40h ; caps lock state has been toggled  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE 1-2 = 0020 num_state equ 20h ; num lock state has been toggled = 0010 scroll_state equ 10h ; scroll lock state has been toggled = 0008 alt_shift equ 08h ; alternate shift key depressed = 0004 ctl_shift equ 04h ; control shift key depressed = 0002 left_shift equ 02h ; left shift key depressed = 0001 right_shift equ 01h ; right shift key depressed ; ...scan codes = 0045 num_key equ 69 = 0046 scroll_key equ 70 = 0038 alt_key equ 56 = 001D ctl_key equ 29 = 003A caps_key equ 58 = 002A left_key equ 42 = 0036 right_key equ 54 = 0052 ins_key equ 82 = 0053 del_key equ 83 0017 biosdata ends 0000 keylocs segment para public 'CODE' assume cs:keylocs 0000 4B 45 59 4C 4F 43 keyloc_ident db 'KEYLOC' = 0006 ident_length equ 6 0006 ikeyloc proc far ; interupt entry point 0006 FB sti ; begin copy of ROM BIOS 0007 50 push ax 0008 53 push bx 0009 51 push cx 000A 52 push dx 000B 56 push si 000C 57 push di 000D 1E push ds 000E 06 push es 000F FC cld 0010 B8 ---- R mov ax,biosdata 0013 8E D8 mov ds,ax 0015 E4 60 in al,kb_data 0017 50 push ax 0018 E4 61 in al,kb_ctl 001A 8A E0 mov ah,al 001C 0C 80 or al,80h 001E E6 61 out kb_ctl,al 0020 86 E0 xchg ah,al 0022 E6 61 out kb_ctl,al 0024 58 pop ax 0025 8A E0 mov ah,al 0027 3C FF cmp al,0FFh 0029 75 05 jnz keylocpatch 002B EA EC24 ---- R jmp K62 ; End of rom code copy 0030 keylocpatch: 0030 50 push ax assume ds:biosdata 0031 24 7F and al,01111111b ; mask out break indicator 0033 3C 38 cmp al,alt_key 0035 74 12 je alt_in 0037 3C 1D cmp al,ctl_key  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE 1-3 0039 74 30 je ctrl_in 003B 3C 2A cmp al,left_key 003D 74 34 je leftshift_in 003F 3C 36 cmp al,right_key 0041 74 38 je rightshift_in ; ...return to normal bios keyboard routine 0043 58 retbioskey: pop ax 0044 EA E9AF ---- R jmp K16 0049 alt_in: 0049 B0 08 mov al,alt_shift 004B E8 008A R call Depress_lock ; ... if this is a break, enter bios at K23 004E 58 pop ax 004F B4 08 mov ah,alt_shift 0051 A8 80 test al,80h ; if 0053 74 11 jz fi ; . 0055 F6 06 0017 R 08 test kb_flag,alt_shift ; . 005A 75 0A jnz fi ; . ; / break and not depressed ; . 005C 80 0E 0017 R 08 or kb_flag,alt_shift ; . Reset depressed flag 0061 EA EA23 ---- R jmp K23 ; . Return in case using ; . alt keypad entry 0066 fi: ; fi 0066 EA EA5E ---- R jmp K26 006B ctrl_in: 006B B0 04 mov al,ctl_shift 006D E8 008A R call Depress_lock 0070 EB 11 90 jmp retdone 0073 leftshift_in: 0073 B0 02 mov al,left_shift 0075 E8 008A R call Depress_lock 0078 EB 09 90 jmp retdone 007B rightshift_in: 007B B0 01 mov al,right_shift 007D E8 008A R call Depress_lock 0080 EB 01 90 jmp retdone 0083 58 retdone: pop ax 0084 EA EA5E ---- R jmp K26 0089 ikeyloc endp ;--------------------------------------------- ; ; Depress_lock ; ; For keys that normally are depressed and held down ; while another key is depressed. (Cntl for example) ; ; ah input key, with break indicator (80h) ; al contains depressed indicator bit mask ; 0089 ?? Down db ? ; indicates the key is held down 008A Depress_lock proc near 008A 52 push dx 008B F6 C4 80 test ah,80h ; if1  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE 1-4 008E 75 2E jnz fi1 ; . 0090 2E: 84 06 0089 R test Down,al ; . 0095 75 27 jnz fi1 ; . ; / make and not down 0097 84 06 0017 R test kb_flag,al ; . if2 009B 74 14 je else2 ; . . ; . / depressed 009D E8 00E4 R call high_beep ; . . 00A0 E8 0110 R call delay ; . . 00A3 E8 00D6 R call low_beep ; . . 00A6 8A D0 mov dl,al ; . . dl:=depressed bit 00A8 F6 D2 not dl ; . . 00AA 20 16 0017 R and kb_flag,dl ; . . key := not depressed 00AE EB 0E 90 jmp fi1 ; . . 00B1 else2: ; . / not depressed 00B1 E8 00D6 R call low_beep ; . . 00B4 E8 0110 R call delay ; . . 00B7 E8 00E4 R call high_beep ; . . 00BA 08 06 0017 R or kb_flag,al ; . . key := depressed 00BE fi1: ; fi1 fi2 00BE F6 C4 80 test ah,80h ; if5 00C1 75 08 jnz else5 ; . ; / make 00C3 2E: 08 06 0089 R or Down,al ; . down := true 00C8 EB 0A 90 jmp fi5 ; . 00CB else5: ; / break 00CB 8A D0 mov dl,al ; . 00CD F6 D2 not dl ; . 00CF 2E: 20 16 0089 R and Down,dl ; . down := false 00D4 fi5: ; fi5 00D4 5A pop dx 00D5 C3 ret 00D6 Depress_lock endp ;--------------------------------- = 0014 h_cycles equ 20 = 012C h_half equ 300 = 0006 l_cycles equ h_cycles / 3 = 0384 l_half equ h_half * 3 00D6 low_beep proc 00D6 52 push dx 00D7 53 push bx 00D8 BB 0006 mov bx,l_cycles 00DB BA 0384 mov dx,l_half 00DE E8 00F2 R call beep 00E1 5B pop bx 00E2 5A pop dx 00E3 C3 ret 00E4 low_beep endp 00E4 high_beep proc 00E4 52 push dx 00E5 53 push bx 00E6 BB 0014 mov bx,h_cycles 00E9 BA 012C mov dx,h_half 00EC E8 00F2 R call beep  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE 1-5 00EF 5B pop bx 00F0 5A pop dx 00F1 C3 ret 00F2 high_beep endp ;--------------------------------- ; Adapted from BIOS Beep routine ; ; bx = # of cycles ; dx = length of half cycle 00F2 beep proc near 00F2 50 push ax 00F3 51 push cx 00F4 E4 61 in al,kb_ctl 00F6 50 push ax 00F7 k65: 00F7 24 FC and al,0FCh 00F9 E6 61 out kb_ctl,al 00FB 8B CA mov cx,dx 00FD E2 FE k66: loop k66 00FF 0C 02 or al,2 0101 E6 61 out kb_ctl,al 0103 8B CA mov cx,dx 0105 E2 FE k67: loop k67 0107 4B dec bx 0108 75 ED jnz k65 010A 58 pop ax 010B E6 61 out kb_ctl,al 010D 59 pop cx 010E 58 pop ax 010F C3 ret 0110 beep endp ;-------------------------------- 0110 delay proc near 0110 51 push cx 0111 B9 3A98 mov cx,15000 0114 E2 FE loop $ 0116 59 pop cx 0117 C3 ret 0118 delay endp = 0118 ikeylast equ $ ; last location + 1 to remain in memory 0000 stacks segment stack 'STACK' 0000 40 [ db 64 dup('stack ') 73 74 61 63 6B 20 20 20 ] 0200 stacks ends ;------------------------------------- 0118 4B 45 59 4C 4F 43 loaded_mess db 'KEYLOC loaded$' 20 6C 6F 61 64 65 64 24 0126 65 72 72 6F 72 20 err_mess db 'error - KEYLOC is already loaded$' 2D 20 4B 45 59 4C  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE 1-6 4F 43 20 69 73 20 61 6C 72 65 61 64 79 20 6C 6F 61 64 65 64 24 0147 keyloc proc far 0147 1E push ds 0148 2B C0 sub ax,ax 014A 50 push ax 014B 1E push ds ; save program seg ; ...Check to see if a copy of KEYLOC has ; already been loaded by comparing Keyloc_ident ; with the same locations relative the the current ; keyboard interupt routine ( it is pointed to by the ; the keyboard interupt vector) 014C FC cld ; increment assume ds:abso 014D B8 ---- R mov ax,abso 0150 8E D8 mov ds,ax 0152 BE 0000 R mov si,offset keyloc_ident 0155 A1 0026 R mov ax,kb_vector+2 ; segment 0158 8B 3E 0024 R mov di,kb_vector ; offset to ident 015C 83 EF 06 sub di,ident_length 015F 8E C0 mov es,ax assume ds:keylocs 0161 B8 ---- R mov ax,keylocs 0164 8E D8 mov ds,ax 0166 B9 0006 mov cx,ident_length 0169 F2/ A6 repne cmpsb ; ds:[si],es:[di] 016B 83 F9 00 cmp cx,0 ; if 016E 74 09 je NotLoaded ; . ; / already loaded 0170 B4 09 mov ah,9h ; . print string 0172 BA 0126 R mov dx,offset err_mess ; . 0175 CD 21 int 21h ; . 0177 1F pop ds ; . get rid of pseg 0178 CB ret ; . return to DOS 0179 NotLoaded: ; fi ; ...set up keyboard interupt vector 0179 B4 09 mov ah,9h 017B BA 0118 R mov dx,offset loaded_mess 017E CD 21 int 21h assume ds:abso 0180 B8 ---- R mov ax,abso 0183 8E D8 mov ds,ax 0185 B8 0006 R mov ax,offset ikeyloc ; ip 0188 A3 0024 R mov kb_vector,ax 018B B8 ---- R mov ax,seg ikeyloc ; cs 018E A3 0026 R mov kb_vector+2,ax ; ...return to DOS, but leave ikeyloc resident 0191 07 pop es ; get program segment 0192 26: C7 06 0001 0027 mov es:byte ptr 1,27h ; change int 20 to 27 0199 BA 0218 R mov dx,offset ikeylast+100h ; dx:=lastaddr+1+prfx 019C CB ret 019D keyloc endp 019D keylocs ends  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE 1-7 end keyloc  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE Symbols-1 Segments and groups: N a m e Size align combine class ABSO . . . . . . . . . . . . . . 0024 AT 0000 BIOSCODE . . . . . . . . . . . . EC24 AT F000 BIOSDATA . . . . . . . . . . . . 0017 AT 0040 KEYLOCS. . . . . . . . . . . . . 019D PARA PUBLIC 'CODE' STACKS . . . . . . . . . . . . . 0200 PARA STACK 'STACK' Symbols: N a m e Type Value Attr ALT_IN . . . . . . . . . . . . . L NEAR 0049 KEYLOCS ALT_KEY. . . . . . . . . . . . . Number 0038 ALT_SHIFT. . . . . . . . . . . . Number 0008 BEEP . . . . . . . . . . . . . . N PROC 00F2 KEYLOCS Length =001E CAPS_KEY . . . . . . . . . . . . Number 003A CAPS_STATE . . . . . . . . . . . Number 0040 CTL_KEY. . . . . . . . . . . . . Number 001D CTL_SHIFT. . . . . . . . . . . . Number 0004 CTRL_IN. . . . . . . . . . . . . L NEAR 006B KEYLOCS DELAY. . . . . . . . . . . . . . N PROC 0110 KEYLOCS Length =0008 DEL_KEY. . . . . . . . . . . . . Number 0053 DEPRESS_LOCK . . . . . . . . . . N PROC 008A KEYLOCS Length =004C DOWN . . . . . . . . . . . . . . L BYTE 0089 KEYLOCS ELSE2. . . . . . . . . . . . . . L NEAR 00B1 KEYLOCS ELSE5. . . . . . . . . . . . . . L NEAR 00CB KEYLOCS ERR_MESS . . . . . . . . . . . . L BYTE 0126 KEYLOCS FI . . . . . . . . . . . . . . . L NEAR 0066 KEYLOCS FI1. . . . . . . . . . . . . . . L NEAR 00BE KEYLOCS FI5. . . . . . . . . . . . . . . L NEAR 00D4 KEYLOCS HIGH_BEEP. . . . . . . . . . . . N PROC 00E4 KEYLOCS Length =000E H_CYCLES . . . . . . . . . . . . Number 0014 H_HALF . . . . . . . . . . . . . Number 012C IDENT_LENGTH . . . . . . . . . . Number 0006 IKEYLAST . . . . . . . . . . . . Number 0118 KEYLOCS IKEYLOC. . . . . . . . . . . . . F PROC 0006 KEYLOCS Length =0083 INS_KEY. . . . . . . . . . . . . Number 0052 INS_STATE. . . . . . . . . . . . Number 0080 K16. . . . . . . . . . . . . . . L FAR E9AF BIOSCODE K23. . . . . . . . . . . . . . . L FAR EA23 BIOSCODE K26. . . . . . . . . . . . . . . L FAR EA5E BIOSCODE K62. . . . . . . . . . . . . . . L FAR EC24 BIOSCODE K65. . . . . . . . . . . . . . . L NEAR 00F7 KEYLOCS K66. . . . . . . . . . . . . . . L NEAR 00FD KEYLOCS K67. . . . . . . . . . . . . . . L NEAR 0105 KEYLOCS KB_CTL . . . . . . . . . . . . . Number 0061 KB_DATA. . . . . . . . . . . . . Number 0060 KB_FLAG. . . . . . . . . . . . . L BYTE 0017 BIOSDATA KB_VECTOR. . . . . . . . . . . . L DWORD 0024 ABSO KEYLOC . . . . . . . . . . . . . F PROC 0147 KEYLOCS Length =0056 KEYLOCPATCH. . . . . . . . . . . L NEAR 0030 KEYLOCS KEYLOC_IDENT . . . . . . . . . . L BYTE 0000 KEYLOCS LEFTSHIFT_IN . . . . . . . . . . L NEAR 0073 KEYLOCS LEFT_KEY . . . . . . . . . . . . Number 002A LEFT_SHIFT . . . . . . . . . . . Number 0002 LOADED_MESS. . . . . . . . . . . L BYTE 0118 KEYLOCS  The IBM Personal Computer MACRO Assembler 01-05-82 PAGE Symbols-2 LOW_BEEP . . . . . . . . . . . . N PROC 00D6 KEYLOCS Length =000E L_CYCLES . . . . . . . . . . . . Number 0006 L_HALF . . . . . . . . . . . . . Number 0384 NOTLOADED. . . . . . . . . . . . L NEAR 0179 KEYLOCS NUM_KEY. . . . . . . . . . . . . Number 0045 NUM_STATE. . . . . . . . . . . . Number 0020 PORT_B . . . . . . . . . . . . . Number 0060 RETBIOSKEY . . . . . . . . . . . L NEAR 0043 KEYLOCS RETDONE. . . . . . . . . . . . . L NEAR 0083 KEYLOCS RIGHTSHIFT_IN. . . . . . . . . . L NEAR 007B KEYLOCS RIGHT_KEY. . . . . . . . . . . . Number 0036 RIGHT_SHIFT. . . . . . . . . . . Number 0001 SCROLL_KEY . . . . . . . . . . . Number 0046 SCROLL_STATE . . . . . . . . . . Number 0010 TIMER. . . . . . . . . . . . . . Number 0040 Warning Severe Errors Errors 0 0  . . . . . Number 0020 PORT_B .