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External References Read the value of the Scratch Register If the arbitrary value comes back identical UART is 16450 Else UART is 8250 End If End If When written in Pascal, the above algorithm ends up looking like this: const COM1_Addr = $3F8; FCR = 2; IIR = 2; SCR = 7; function IdentifyUART: String; var Test: Byte; begin Port[COM1_Addr + FCR] := $E7; Test := Port[COM1_Addr + IIR]; if (Test and $40) > 0 then if (Test and $80) > 0 then if (Test and $20) > 0 then IdentifyUART := '16750' else IdentifyUART := '16550A' else IdentifyUART := '16550' else begin Port[COM1_Addr + SCR] := $2A; if Port[COM1_Addr + SCR] = $2A then IdentifyUART := '16450' else IdentifyUART := '8250'; end; end; We still havn't identified between the 8250, 8250A, or 8250B; but that is rather pointless anyway on most current computers as it is very unlikely to even find one of those chips because of their age. A very similar procedure can be used to determine the CPU of a computer, but that is beyond the scope of this book. 3.8 External References • History of Interrupt Programming 1 • 8259 Chip Information with other registers explained 2 (dead link?) • Interfacing the Serial / RS232 Port 3 1 http://www.cs.clemson.edu/~mark/interrupts.html 2 http://satyap.csoft.net/8259.html 3 http://www.beyondlogic.org/serial/serial.htm 53
8250 UART Programming While the 8250 is by far the most popular UART on desktop computers, other popular UARTs include: • the UART inside the Atmel AVR 4 : ... Embedded_Systems/Atmel_AVR#Serial_- Communication 5 • the UART inside the Microchip PIC 6 : "Microchip AN774: Asynchronous Communications with the PICmicro® USART" 7 • the UART inside the Apple Macintosh: ... • "bit-banging" a UART: ... http://microchip.com/stellent/idcplg?IdcService=SS_ GET_PAGE&nodeId=1824&appnote=en012058 3.9 Other Serial Programming Articles Category:Serial Programming 8 4 http://en.wikibooks.org/wiki/Embedded_Systems%2FAtmel_AVR 5 http://en.wikibooks.org/wiki/Embedded_Systems%2FAtmel_AVR%23Serial_Communication 6 http://en.wikibooks.org/wiki/PIC http://microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote= 7 en012073 8 http://en.wikibooks.org/wiki/Category%3ASerial%20Programming 54
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Serial Programming Wikibooks.org
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Contents 1 Introduction and OSI Mod
Page 6 and 7: 1 Introduction and OSI Model 1.1 In
Page 8 and 9: Software Examples • Serial Networ
Page 10 and 11: 2 RS-232 Connections 2.1 Introducti
Page 12 and 13: Data Terminal/Communications Equipm
Page 14 and 15: Data Terminal/Communications Equipm
Page 16 and 17: Connection Types Figure 1 Female DB
Page 18 and 19: Connection Types Figure 5 mini-ster
Page 20 and 21: Wiring Pins Explained One thing to
Page 22 and 23: Baud Rates Explained 2.4.9 RI (Ring
Page 24 and 25: Baud Rates Explained 2.5.1 Modems E
Page 26 and 27: Signal Bits 2.6.3 Parity Bit To hel
Page 28 and 29: External References Baud Rate Maxim
Page 30 and 31: 3 8250 UART Programming 3.1 Introdu
Page 32 and 33: 8086 I/O ports char test; test = 25
Page 34 and 35: x86 Processor Interrupts 3.3.2 Inte
Page 36 and 37: 8259 PIC (Programmable Interrupt Co
Page 38 and 39: Serial COM Port Memory and I/O Allo
Page 40 and 41: UART Registers UART Registers Base
Page 42 and 43: UART Registers Divisor Latch Byte V
Page 44 and 45: UART Registers The Received Data in
Page 46 and 47: UART Registers When you are writing
Page 48 and 49: UART Registers these to a logical "
Page 50 and 51: UART Registers Each bit the data po
Page 52 and 53: UART Registers Line Status Register
Page 54 and 55: UART Registers Bits 7 and 6 are dir
Page 58 and 59: 4 Serial DOS 4.1 Introduction It is
Page 60 and 61: Finding the Port I/O Address for th
Page 62 and 63: Making modifications to UART Regist
Page 64 and 65: Basic Serial Input 4.5.1 Polling th
Page 66 and 67: Interrupt Drivers in DOS 4.6 Interr
Page 68 and 69: Interrupt Drivers in DOS able to us
Page 70 and 71: Interrupt Drivers in DOS Interrupt
Page 72 and 73: Terminal Program Revisited Port[Com
Page 74 and 75: Terminal Program Revisited RBR = 0;
Page 76: Terminal Program Revisited build a
Page 79 and 80: Serial Linux Classic Unix systems o
Page 81 and 82: Serial Linux 1. Terminals/teletypes
Page 83 and 84: Serial Linux for more information t
Page 85 and 86: Serial Linux signal and trap that s
Page 87 and 88: Serial Linux 5.2.6 uucp Overview Uu
Page 90 and 91: 6 Serial Java 6.1 Using Java for Se
Page 92 and 93: Using Java for Serial Communication
Page 94 and 95: JavaComm API 6.2.2 Download & Insta
Page 96 and 97: JavaComm API wantedPortName); Syste
Page 98 and 99: JavaComm API 6.2.4 Simple Data Tran
Page 100 and 101: JavaComm API Before going into deta
Page 102 and 103: JavaComm API // makes sense to enab
Page 104 and 105: JavaComm API /** * Clear the buffer
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JavaComm API } } start = i; } retur
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RxTx Like with any other particular
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See also • SerialIO has a free tr
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Forming Data Packets • The footer
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Forming Data Packets bitrate or raw
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8 Error Correction Methods 8.1 Intr
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ACK-NAK A 1-bit sequence number (al
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combination If it sends a message b
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9 Appendex A:Modems and AT Commands
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Introduction forms the base for pro
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Introduction can still also be used
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Modem Programming Basics • By loo
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Modem Programming Basics Whatever i
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Modem Programming Basics 9.2.5 Char
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Changing State 9.4 Changing State 9
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AT Commands with the exception of #
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Result Codes Description: Result
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10 Contributors Edits User 10 Adrig
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List of Figures • GFDL: Gnu Free
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List of Figures 1 GFDL 2 User Mike1
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from that copyright holder, and you
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