source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Device/Serial/SerialCommand.asm@ 221

Last change on this file since 221 was 220, checked in by gregli@…, 13 years ago

Serial port code, removed pointer re(normalization) code as the pointer is normalized before we are called and the sector count is kept in the range where we will not need to renormalize.
File size: 23.7 KB
Line 
1; Project name : XTIDE Universal BIOS
2; Description : Serial Device Command functions.
3
4; Section containing code
5SECTION .text
6
7;--------------- UART Equates -----------------------------
8;
9; Serial Programming References:
10; http://en.wikibooks.org/wiki/Serial_Programming
11;
12
13SerialCommand_UART_base EQU 0
14SerialCommand_UART_transmitByte EQU 0
15SerialCommand_UART_receiveByte EQU 0
16
17;
18; Values for UART_divisorLow:
19; 60h = 1200, 30h = 2400, 18h = 4800, 0ch = 9600, 6 = 19200, 3 = 38400, 2 = 57600, 1 = 115200
20;
21SerialCommand_UART_divisorLow EQU 0
22
23;
24; We support 4 baud rates, starting here going higher and skipping every other baud rate
25; Starting with 30h, that means 30h (1200 baud), 0ch (9600 baud), 3 (38400 baud), and 1 (115200 baud)
26; Note: hardware baud multipliers (2x, 4x) will impact the final baud rate and are not known at this level
27;
28SerialCommand_UART_divisorLow_startingBaud EQU 030h
29
30SerialCommand_UART_interruptEnable EQU 1
31
32;
33; UART_divisorHigh is zero for all speeds including and above 1200 baud (which is all we do)
34;
35SerialCommand_UART_divisorHigh EQU 1
36
37SerialCommand_UART_interruptIdent EQU 2
38SerialCommand_UART_FIFOControl EQU 2
39
40SerialCommand_UART_lineControl EQU 3
41
42SerialCommand_UART_modemControl EQU 4
43
44SerialCommand_UART_lineStatus EQU 5
45
46SerialCommand_UART_modemStatus EQU 6
47
48SerialCommand_UART_scratch EQU 7
49
50SerialCommand_Protocol_Write EQU 3
51SerialCommand_Protocol_Read EQU 2
52SerialCommand_Protocol_Inquire EQU 0
53SerialCommand_Protocol_Header EQU 0a0h
54
55;--------------------------------------------------------------------
56; SerialCommand_OutputWithParameters
57; Parameters:
58; BH: Non-zero if 48-bit addressing used
59; (ignored at present as 48-bit addressing is not supported)
60; BL: IDE Status Register bit to poll after command
61; (ignored at present, since there is no IDE status register to poll)
62; ES:SI: Ptr to buffer (for data transfer commands)
63; DS:DI: Ptr to DPT (in RAMVARS segment)
64; SS:BP: Ptr to IDEREGS_AND_INTPACK
65; Returns:
66; AH: INT 13h Error Code
67; CF: Cleared if success, Set if error
68; Corrupts registers:
69; AL, BX, CX, DX, (ES:SI for data transfer commands)
70;--------------------------------------------------------------------
71ALIGN JUMP_ALIGN
72SerialCommand_OutputWithParameters:
73
74 mov ah,(SerialCommand_Protocol_Header | SerialCommand_Protocol_Read)
75
76 mov al,[bp+IDEPACK.bCommand]
77
78 cmp al,20h ; Read Sectors IDE command
79 jz .readOrWrite
80 inc ah ; now SerialCommand_Protocol_Write
81 cmp al,30h ; Write Sectors IDE command
82 jz .readOrWrite
83
84; all other commands return success
85; including function 0ech which should return drive information, this is handled with the identify functions
86;
87 xor ah,ah ; also clears carry
88 ret
89
90.readOrWrite:
91 mov [bp+IDEPACK.bFeatures],ah ; store protocol command
92
93 mov dl, byte [di+DPT.bSerialPortAndBaud]
94
95; fall-through
96
97;--------------------------------------------------------------------
98; SerialCommand_OutputWithParameters_DeviceInDL
99; Parameters:
100; AH: Protocol Command
101; DL: Packed I/O port and baud rate
102; ES:SI: Ptr to buffer (for data transfer commands)
103; SS:BP: Ptr to IDEREGS_AND_INTPACK
104; Returns:
105; AH: INT 13h Error Code
106; CF: Cleared if success, Set if error
107; Corrupts registers:
108; AL, BX, CX, DX, (ES:SI for data transfer commands)
109;--------------------------------------------------------------------
110SerialCommand_OutputWithParameters_DeviceInDL:
111
112 push si
113 push di
114 push bp
115 push es
116
117;
118; Unpack I/O port and baud from DPT
119; Port to DX more or less for the remainder of the routine
120; Baud in CH until UART initialization is complete
121;
122 mov dh, ((DEVICE_SERIAL_PACKEDPORTANDBAUD_STARTINGPORT & 0f00h) >> (8+1))
123 shl dx, 1 ; port offset already x4, needs one more shift to be x8
124 mov cl, dl
125
126 and cl, (DEVICE_SERIAL_PACKEDPORTANDBAUD_BAUDMASK << 1)
127 mov ch, SerialCommand_UART_divisorLow_startingBaud
128 shr ch, cl
129 adc ch, 0
130
131 and dl, ((DEVICE_SERIAL_PACKEDPORTANDBAUD_PORTMASK << 1) & 0ffh)
132 add dx, byte (DEVICE_SERIAL_PACKEDPORTANDBAUD_STARTINGPORT & 0ffh)
133
134 mov al,[bp+IDEPACK.bSectorCount]
135
136;
137; Command byte and sector count live at the top of the stack, pop/push are used to access
138;
139 push ax
140
141%if 0
142 cld ; Shouldn't be needed. DF has already been cleared (line 24, Int13h.asm)
143%endif
144
145;----------------------------------------------------------------------
146;
147; Initialize UART
148;
149; We do this each time since DOS (at boot) or another program may have
150; decided to reprogram the UART
151;
152 mov bl,dl ; setup BL with proper values for read/write loops (BH comes later)
153
154 mov al,83h
155 add dl,SerialCommand_UART_lineControl
156 out dx,al
157
158 mov al,ch
159 mov dl,bl ; divisor low
160 out dx,al
161
162 xor ax,ax
163 inc dx ; divisor high
164 push dx
165 out dx,al
166
167 mov al,047h
168 inc dx ; fifo
169 out dx,al
170
171 mov al,03h
172 inc dx ; linecontrol
173 out dx,al
174
175 mov al,0bh
176 inc dx ; modemcontrol
177 out dx,al
178
179 inc dx ; linestatus (no output now, just setting up BH for later use)
180 mov bh,dl
181
182 pop dx ; base, interrupts disabled
183 xor ax,ax
184 out dx,al
185
186;----------------------------------------------------------------------
187;
188; Send Command
189;
190; Sends first six bytes of IDEREGS_AND_INTPACK as the command
191;
192 push es ; save off real buffer location
193 push si
194
195 mov si,bp ; point to IDEREGS for command dispatch;
196 push ss
197 pop es
198
199 mov di,0ffffh ; initialize checksum for write
200 mov bp,di
201
202 mov cx,4 ; writing 3 words (plus 1)
203
204 cli ; interrupts off...
205
206 call SerialCommand_WriteProtocol.entry
207
208 pop di ; restore real buffer location (note change from SI to DI)
209 ; Buffer is primarily referenced through ES:DI throughout, since
210 ; we need to store (read sector) faster than we read (write sector)
211 pop es
212
213%if 0
214;;; no longer needed, since the pointer is normalized before we are called and we do not support
215;;; more than 128 sectors (and for 128 specifically, the pointer must be segment aligned).
216;;; See comments below at the point this entry point was called for more details...
217.nextSectorNormalize:
218 call Registers_NormalizeESDI
219%endif
220
221 pop ax ; load command byte (done before call to .nextSector on subsequent iterations)
222 push ax
223
224;
225; Top of the read/write loop, one iteration per sector
226;
227.nextSector:
228 mov si,0ffffh ; initialize checksum for read or write
229 mov bp,si
230
231 mov cx,0101h ; writing 256 words (plus 1)
232
233 shr ah,1 ; command byte, are we doing a write?
234 jnc .readEntry
235
236 xchg si,di
237 call SerialCommand_WriteProtocol.entry
238 xchg si,di
239
240 inc cx ; CX = 1 now (0 out of WriteProtocol)
241 jmp .readEntry
242
243;----------------------------------------------------------------------
244;
245; Timeout
246;
247; To save code space, we use the contents of DL to decide which byte in the word to return for reading.
248;
249.readTimeout:
250 push ax ; not only does this push preserve AX (which we need), but it also
251 ; means the stack has the same number of bytes on it as when we are
252 ; sending a packet, important for error cleanup and exit
253 mov ah,1
254 call SerialCommand_WaitAndPoll_Read
255 pop ax
256 test dl,1
257 jz .readByte1Ready
258 jmp .readByte2Ready
259
260;----------------------------------------------------------------------------
261;
262; Read Block (without interrupts, used when there is a FIFO, high speed)
263;
264; NOTE: This loop is very time sensitive. Literally, another instruction
265; cannot be inserted into this loop without us falling behind at high
266; speed (460.8K baud) on a 4.77Mhz 8088, making it hard to receive
267; a full 512 byte block.
268;
269.readLoop:
270 stosw ; store word in caller's data buffer
271
272 add bp, ax ; update Fletcher's checksum
273 adc bp, 0
274 add si, bp
275 adc si, 0
276
277.readEntry:
278 mov dl,bh
279 in al,dx
280 shr al,1 ; data ready (byte 1)?
281 mov dl,bl ; get ready to read data
282 jnc .readTimeout ; nope not ready, update timeouts
283
284;
285; Entry point after initial timeout. We enter here so that the checksum word
286; is not stored (and is left in AX after the loop is complete).
287;
288.readByte1Ready:
289 in al, dx ; read data byte 1
290
291 mov ah, al ; store byte in ah for now
292
293;
294; note the placement of this reset of dl to bh, and that it is
295; before the return, which is assymetric with where this is done
296; above for byte 1. The value of dl is used by the timeout routine
297; to know which byte to return to (.read_byte1_ready or
298; .read_byte2_ready)
299;
300 mov dl,bh
301
302 in al,dx
303 shr al,1 ; data ready (byte 2)?
304 jnc .readTimeout
305.readByte2Ready:
306 mov dl,bl
307 in al, dx ; read data byte 2
308
309 xchg al, ah ; ah was holding byte 1, reverse byte order
310
311 loop .readLoop
312
313 sti ; interrupts back on ASAP, between packets
314
315;
316; Compare checksums
317;
318 xchg ax,bp
319 xor ah,al
320 mov cx,si
321 xor cl,ch
322 mov al,cl
323 cmp ax,bp
324 jnz SerialCommand_OutputWithParameters_Error
325
326 pop ax ; sector count and command byte
327 dec al ; decrememnt sector count
328 push ax ; save
329 jz SerialCommand_OutputWithParameters_ReturnCodeInALCF ; CF=0 from "cmp ax,bp" returning Zero above
330
331 cli ; interrupts back off for ACK byte to host
332 ; (host could start sending data immediately)
333 out dx,al ; ACK with next sector number
334
335%if 0
336;;; This code is no longer needed as we do not support more than 128 sectors, and for 128 the pointer
337;;; must be segment aligned. If we ever do want to support more sectors, the code can help...
338
339;
340; Normalize buffer pointer for next go round, if needed.
341;
342; We need to re-nomrlize the pointer in ES:DI after processing every 7f sectors. That number could
343; have been 80 if we knew the offset was on a segment boundary, but this may not be the case.
344;
345; We re-normalize based on the sector count (flags from "dec al" above)...
346; a) we normalize before the first sector goes out, immediately after sending the command packet (above)
347; b) on transitions from FF to FE, very rare case for writing 255 or 256 sectors
348; c) on transitions from 80 to 7F, a large read/write
349; d) on transitions from 00 to FF, very, very rare case of writing 256 secotrs
350; We don't need to renormalize in this case, but it isn't worth the memory/effort to not do
351; the extra work, and it does no harm.
352;
353; I really don't care much about (d) because I have not seen cases where any OS makes a request
354; for more than 127 sectors. Back in the day, it appears that some BIOS could not support more than 127
355; sectors, so that may be the practical limit for OS and application developers. The Extended BIOS
356; function also appear to be capped at 127 sectors. So although this can support the full 256 sectors
357; if needed, we are optimized for that 1-127 range.
358;
359; Assume we start with 0000:000f, with 256 sectors to write...
360; After first packet, 0000:020f
361; First decrement of AL, transition from 00 to FF: renormalize to 0020:000f (unnecessary)
362; After second packet, 0020:020f
363; Second derement of AL, transition from FF to FE: renormalize to 0040:000f
364; After 7f more packets, 0040:fe0f
365; Decrement of AL, transition from 80 to 7F: renormalize to 1020:000f
366; After 7f more packets, 1020:fe0f or 2000:000f if normalized
367; Decrement of AL, from 1 to 0: exit
368;
369 jge short .nextSector ; OF=SF, branch for 1-7e, most common case
370 ; (0 kicked out above for return success)
371
372 add al,2 ; 7f-ff moves to 81-01
373 ; (0-7e kicked out before we get here)
374 ; 7f moves to 81 and OF=1, so OF=SF
375 ; fe moves to 0 and OF=0, SF=0, so OF=SF
376 ; ff moves to 1 and OF=0, SF=0, so OF=SF
377 ; 80-fd moves to 82-ff and OF=0, so OF<>SF
378
379 jl short .nextSector ; OF<>SF, branch for all cases but 7f, fe, and ff
380
381; jpo short .nextSector ; if we really wanted to avoid normalizing for ff, this
382 ; is one way to do it, but it adds more memory and more
383 ; cycles for the 7f and fe cases. IMHO, given that I've
384 ; never seen a request for more than 7f, this seems unnecessary.
385
386 jmp short .nextSectorNormalize ; our two renormalization cases (plus one for ff)
387
388%else
389
390 jmp short .nextSector
391
392%endif
393
394;---------------------------------------------------------------------------
395;
396; Cleanup, error reporting, and exit
397;
398
399;
400; Used in situations where a call is underway, such as with SerialCommand_WaitAndPoll
401;
402ALIGN JUMP_ALIGN
403SerialCommand_OutputWithParameters_ErrorAndPop4Words:
404 add sp,8
405;;; fall-through
406
407ALIGN JUMP_ALIGN
408SerialCommand_OutputWithParameters_Error:
409;----------------------------------------------------------------------
410;
411; Clear read buffer
412;
413; In case there are extra characters or an error in the FIFO, clear it out.
414; In theory the initialization of the UART registers above should have
415; taken care of this, but I have seen cases where this is not true.
416;
417.clearBuffer:
418 mov dl,bh
419 in al,dx
420 mov dl,bl
421 test al,08fh
422 jz .clearBufferComplete
423 shr al,1
424 in al,dx
425 jc .clearBuffer ; note CF from shr above
426
427.clearBufferComplete:
428 stc
429 mov al,1
430
431ALIGN JUMP_ALIGN
432SerialCommand_OutputWithParameters_ReturnCodeInALCF:
433%if 0
434 sti ; all paths here will already have interrupts turned back on
435%endif
436 mov ah,al
437
438 pop bp ; recover ax (command and count) from stack, throw away
439
440 pop es
441 pop bp
442 pop di
443 pop si
444
445 ret
446
447;--------------------------------------------------------------------
448; SerialCommand_WriteProtocol
449;
450; NOTE: As with its read counterpart, this loop is very time sensitive.
451; Although it will still function, adding additional instructions will
452; impact the write througput, especially on slower machines.
453;
454; Parameters:
455; ES:SI: Ptr to buffer
456; CX: Words to write, plus 1
457; BP/DI: Initialized for Checksum (-1 in each)
458; DH: I/O Port high byte
459; BX: LineStatus Register address (BH) and Receive/Transmit Register address (BL)
460; Returns:
461; BP/DI: Checksum for written bytes, compared against ACK from server in .readLoop
462; CX: Zero
463; DL: Receive/Transmit Register address
464; Corrupts registers:
465; AX
466;--------------------------------------------------------------------
467ALIGN JUMP_ALIGN
468SerialCommand_WriteProtocol:
469.writeLoop:
470 es lodsw ; fetch next word
471
472 out dx,al ; output first byte
473
474 add bp,ax ; update checksum
475 adc bp,0
476 add di,bp
477 adc di,0
478
479 mov dl,bh ; transmit buffer empty?
480 in al,dx
481 test al,20h
482 jz .writeTimeout2 ; nope, use our polling routine
483
484.writeByte2Ready:
485 mov dl,bl
486 mov al,ah ; output second byte
487 out dx,al
488
489.entry:
490 mov dl,bh ; transmit buffer empty?
491 in al,dx
492 test al,20h
493 mov dl,bl
494 jz .writeTimeout1 ; nope, use our polling routine
495
496.writeByte1Ready:
497 loop .writeLoop
498
499 mov ax,di ; fold Fletcher's checksum and output
500 xor al,ah
501 out dx,al ; byte 1
502
503 call SerialCommand_WaitAndPoll_Write
504
505 mov ax,bp
506 xor al,ah
507 out dx,al ; byte 2
508
509 ret
510
511.writeTimeout2:
512 mov dl,ah ; need to preserve AH, but don't need DL (will be reset upon return)
513 call SerialCommand_WaitAndPoll_Write
514 mov ah,dl
515 jmp .writeByte2Ready
516
517.writeTimeout1:
518 mov ax,.writeByte1Ready
519 push ax ; return address for ret at end of SC_writeTimeout2
520;;; fall-through
521
522;--------------------------------------------------------------------
523; SerialCommand_WaitAndPoll
524;
525; Parameters:
526; AH: UART_LineStatus bit to test (20h for write, or 1h for read)
527; One entry point fills in AH with 20h for write
528; DX: Port address (OK if already incremented to UART_lineStatus)
529; BX:
530; Stack: 2 words on the stack below the command/count word
531; Returns:
532; Returns when desired UART_LineStatus bit is cleared
533; Jumps directly to error exit if timeout elapses (and cleans up stack)
534; Corrupts registers:
535; AX
536;--------------------------------------------------------------------
537
538SerialCommand_WaitAndPoll_SoftDelayTicks EQU 20
539
540ALIGN JUMP_ALIGN
541SerialCommand_WaitAndPoll_Write:
542 mov ah,20h
543;;; fall-through
544
545ALIGN JUMP_ALIGN
546SerialCommand_WaitAndPoll_Read:
547 push cx
548 push dx
549
550;
551; We first poll in a tight loop, interrupts off, for the next character to come in/be sent
552;
553 xor cx,cx
554.readTimeoutLoop:
555 mov dl,bh
556 in al,dx
557 test al,ah
558 jnz .readTimeoutComplete
559 loop .readTimeoutLoop
560
561;
562; If that loop completes, then we assume there is a long delay involved, turn interrupts back on
563; and wait for a given number of timer ticks to pass.
564;
565 sti
566 mov cl,SerialCommand_WaitAndPoll_SoftDelayTicks
567 call Timer_InitializeTimeoutWithTicksInCL
568.WaitAndPoll:
569 call Timer_SetCFifTimeout
570 jc SerialCommand_OutputWithParameters_ErrorAndPop4Words
571 in al,dx
572 test al,ah
573 jz .WaitAndPoll
574 cli
575
576.readTimeoutComplete:
577 pop dx
578 pop cx
579 ret
580
581;--------------------------------------------------------------------
582; SerialCommand_IdentifyDeviceToBufferInESSIwithDriveSelectByteInBH
583; Parameters:
584; BH: Drive Select byte for Drive and Head Select Register
585; DS: Segment to RAMVARS
586; ES:SI: Ptr to buffer to receive 512-byte IDE Information
587; CS:BP: Ptr to IDEVARS
588; Returns:
589; AH: INT 13h Error Code
590; NOTE: Not set (or checked) during drive detection
591; CF: Cleared if success, Set if error
592; Corrupts registers:
593; AL, BL, CX, DX, SI, DI, ES
594;--------------------------------------------------------------------
595ALIGN JUMP_ALIGN
596SerialCommand_IdentifyDeviceToBufferInESSIwithDriveSelectByteInBH:
597;
598; To improve boot time, we do our best to avoid looking for slave serial drives when we already know the results
599; from the looking for a master. This is particuarly true when doing a COM port scan, as we will end up running
600; through all the COM ports and baud rates a second time.
601;
602; But drive detection isn't the only case - we also need to get the right drive when called on int13h/25h.
603;
604; The decision tree:
605;
606; Master:
607; bSerialPackedPortAndBaud Non-Zero: -> Continue with bSerialPackedAndBaud (1)
608; bSerialPackedPortAndBaud Zero:
609; bLastSerial Zero: -> Scan (2)
610; bLastSerial Non-Zero: -> Continue with bLastSerial (3)
611;
612; Slave:
613; bSerialPackedPortAndBaud Non-Zero:
614; bLastSerial Zero: -> Error - Not Found (4)
615; bLastSerial Non-Zero: -> Continue with bSerialPackedAndBaud (5)
616; bSerialPackedPortAndBaud Zero:
617; bLastSerial Zero: -> Error - Not Found (4)
618; bLastSerial Non-Zero: -> Continue with bLastSerial (6)
619;
620; (1) This was a port/baud that was explicilty set with the configurator. In the drive detection case, as this
621; is the Master, we are checking out a new controller, and so don't care about the value of bLastSerial.
622; And as with the int13h/25h case, we just go off and get the needed information using the user's setting.
623; (2) We are using the special .ideVarsSerialAuto strucutre. During drive detection, we would only be here
624; if bLastSerial is zero (since we only scan if no explicit drives are set), so we go off to scan.
625; (3) We are using the special .ideVarsSerialAuto strucutre. We won't get here during drive detection, but
626; we might get here on an int13h/25h call. If we have scanned COM drives, they are the ONLY serial drives
627; in use, and so bLastSerial will reflect the port/baud setting for the scanned COM drives.
628; (4) No master has been found yet, therefore no slave should be found. Avoiding the slave reduces boot time,
629; especially in the full COM port scan case. Note that this is different from the hardware IDE, where we
630; will scan for a slave even if a master is not present. Note that if ANY master had been previously found,
631; we will do the slave scan, which isn't harmful, it just wates time. But the most common case (by a wide
632; margin) will be just one serial controller.
633; (5) A COM port scan for a master had been previously completed, and a drive was found. In a multiple serial
634; controller scenario being called with int13h/25h, we need to use the value in bSerialPackedPortAndBaud
635; to make sure we get the proper drive.
636; (6) A COM port scan for a master had been previously completed, and a drive was found. We would only get here
637; if no serial drive was explicitly set by the user in the configurator or that drive had not been found.
638; Instead of performing the full COM port scan for the slave, use the port/baud value stored during the
639; master scan.
640;
641 mov dl,[cs:bp+IDEVARS.bSerialPackedPortAndBaud]
642 mov al, byte [RAMVARS.xlateVars+XLATEVARS.bLastSerial]
643
644 test bh, FLG_DRVNHEAD_DRV
645 jz .master
646
647 test al,al ; Take care of the case that is different between master and slave.
648 jz .error ; Because we do this here, the jz after the "or" below will not be taken
649
650; fall-through
651.master:
652 test dl,dl
653 jnz .identifyDeviceInDL
654
655 or dl,al ; Move bLast into position in dl, as well as test for zero
656 jz .scanSerial
657
658; fall-through
659.identifyDeviceInDL:
660
661 push bp ; setup fake IDEREGS_AND_INTPACK
662
663 push dx
664
665 mov cl,1 ; 1 sector to move
666 push cx
667
668 mov bl,0a0h ; protocol command to ah and onto stack with bh
669 mov ah,bl
670
671 push bx
672
673 mov bp,sp
674 call SerialCommand_OutputWithParameters_DeviceInDL
675
676 pop bx
677
678 pop cx
679 pop dx
680
681 pop bp
682;
683; place packed port/baud in RAMVARS, read by FinalizeDPT and DetectDrives
684;
685; Note that this will be set during an int13h/25h call as well. Which is OK since it is only used (at the
686; top of this routine) for drives found during a COM scan, and we only COM scan if there were no other
687; COM drives found. So we will only reaffirm the port/baud for the one COM port/baud that has a drive.
688;
689 jc .notFound ; only store bLastSerial if success
690 mov byte [RAMVARS.xlateVars+XLATEVARS.bLastSerial], dl
691
692.notFound:
693 ret
694
695;----------------------------------------------------------------------
696;
697; SerialCommand_AutoSerial
698;
699; When the SerialAuto IDEVARS entry is used, scans the COM ports on the machine for a possible serial connection.
700;
701
702.scanPortAddresses: db DEVICE_SERIAL_COM7 >> 2
703 db DEVICE_SERIAL_COM6 >> 2
704 db DEVICE_SERIAL_COM5 >> 2
705 db DEVICE_SERIAL_COM4 >> 2
706 db DEVICE_SERIAL_COM3 >> 2
707 db DEVICE_SERIAL_COM2 >> 2
708 db DEVICE_SERIAL_COM1 >> 2
709 db 0
710
711ALIGN JUMP_ALIGN
712.scanSerial:
713 mov di,.scanPortAddresses-1
714
715.nextPort:
716 inc di ; load next port address
717 mov dl,[cs:di]
718
719 mov dh,0 ; shift from one byte to two
720 eSHL_IM dx, 2
721 jz .error
722
723;
724; Test for COM port presence, write to and read from registers
725;
726 push dx
727 add dl,SerialCommand_UART_lineControl
728 mov al, 09ah
729 out dx, al
730 in al, dx
731 pop dx
732 cmp al, 09ah
733 jnz .nextPort
734
735 mov al, 0ch
736 out dx, al
737 in al, dx
738 cmp al, 0ch
739 jnz .nextPort
740
741;
742; Pack into dl, baud rate starts at 0
743;
744 add dx,-(DEVICE_SERIAL_PACKEDPORTANDBAUD_STARTINGPORT)
745 shr dx,1 ; dh is zero at this point, and will be sent to the server,
746 ; so we know this is an auto detect
747
748 jmp .testFirstBaud
749
750;
751; Walk through 4 possible baud rates
752;
753.nextBaud:
754 inc dx
755 test dl,3
756 jz .nextPort
757
758.testFirstBaud:
759 call .identifyDeviceInDL
760 jc .nextBaud
761
762 ret
763
764.error:
765 stc
766%if 0
767 mov ah,1 ; setting the error code is unnecessary as this path can only be taken during
768 ; drive detection, and drive detection works off CF and does not check AH
769%endif
770 ret
771
772
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