Serial Devices

1. Serial Devices • Serial Standards • RS-232 • RS-232 cables consist of up to 25 wires, each with a specific function and each intended to carry a different signal. • Two for data transmission • The rest are for various kinds of control signals • All 25 pins are rarely used • Only 9 pins commonly • DB25-to-9 pin adapters are readily available Serial Devices

2. Serial Devices • RS-232 standard defines two types of equipment • Data Terminal Equipment (DTE) • Computers are DTE • Data Communication Equipment (DCT) • Modems, printers are DCE • DTE uses pin2 to transmit data and pin 3 to receive data; DCE does the reverse • To connect a computer to a modem, you want to make the connection straight through. • To connect a computer to a computer (DTE<->DTE), you need a able with receive/transmit lines crossed. • Called a null-modem or modem-eliminator cable Serial Devices

3. Serial Devices • connectors • DB-25 • Mini DIN-8 • Found on Macs, laptops and workstations. • DB-9 variant • Commonly found on PCs • RJ-45 variant • An eight-wire modular telephone connector • Used as intermediate connectors when routing serial lines through patch panels. • Terminal servers Serial Devices

4. Configuration of hardwired terminals • Terminal configuration involves main tasks • Making sure a process is attached to a terminal to accept logins • Making sure that information about the terminal is available once a user has logged in. • The login process • Usually, Init daemon spawn a process (getty) on each terminal port that is turned on in /etc/inittab • Getty set the port’s initial characteristics and print a login prompt Serial Devices

5. Configuration of hardwired terminals • The sequence of events in a complete login • A user enters a login name at getty’s prompt • Getty executes the login program with the specified name • Login request a password and validate it again /etc/passwd • Login print the message of the day from /etc/motd • Login sets up the TERM env and runs a shell • The shell executes the appropriate startup files • The shell prints a prompt and waits for input. • When user logout, control returns to init, which wakes up and spawn a new getty on the terminal port. Serial Devices

6. Configuration of hardwired terminals • Possible related files • BSD: The /etc/ttys and /etc/ttytab files • Format • Device program termtype {on|off} [secure] • /etc/ttytype • /etc/getttytab • Solaris/HP-UX: /etc/inittab • /etc/gettydefs • Starting the terminal line • Force the program init to reread the terminal line initialization information • Init becomes aware the device that has been added • Init takes the appropriate action (getty) • Example • #telinit q Serial Devices

7. Terminal-Related Special Files • Special files for serial lines • Vary between systems • often the form /dev/ttyn where n is a number corresponding the line number • Pseudo terminal devices - Indirect login session via a network or windowing system • The master or control pseudo terminal, /dev/pty[p-s]n • The slave pseudo terminal ( virtual terminal) /dev/ttp[p-s]n • The special file /dev/console always refers to the system console device. Serial Devices

8. Terminals • Commands tty • Display what special file is being used for any login session. • Example: [ruihong@dafinn ~]$ tty /dev/pts/3 • Specifying Terminal Characteristics • Unix programs are generally written to be terminal independent • They call standard screen manipulation library which is responsible for interfacing to actual terminals. • The library serve to map terminal characteristics and functions to the specific character sequences required to perform them on any specific terminal. Serial Devices

9. Terminals • Terminal definitions are stored in database • User set what kind of terminal they are using by setting the TERM environment • Terminal definition database • Under BSD scheme, /etc/termcap • A text file consisting series entries that describes how different terminals function • Such as How many columns, how many lines, auto wrapping, characters sequence when a special key is pressed • Under System V, /usr/share/lib/terminfo • A series of binary files describing terminal capabilities • Each entry is a separate file in the subdirectory of /usr/share/lib/terminfo/{firstletter}/file Serial Devices

10. Terminals • Terminfo files are compiled from source code • Command to manipulating terminfo entries • Compile terminfo source: tic • List source for a compiled terminfo entry: infocmp • Translate from terminfo to termcap: infocmp –C • Translate from termcap to terminfo source: captoinfo • For example: To use a old terminal for AIX system where system does no have terminfo entry for it. • found a BSD termcap • copy it to the system • run captoinfo • compile it using tic Serial Devices

11. STTY: set terminal options • Specify generic terminal and terminal line characteristics • Syntax: stty option [value] … • See next page for commonly used options • Display the current terminal settings • $stty –a • Stty controls device driver and allow user to explicitly change the default setting Serial Devices

12. Commonly used stty options Serial Devices

13. Modems • Modem • converts digital signal from computer to analog signal for transmission on a standard phone line. • Internal and external modem • External:RS-232 interface on the digital side and RJ-11 jack on the analog side • Internal:pluginto an ISA, PCI or PCMCIA slot and have a RJ-11 jack • Upto 56Kb/s throughput Serial Devices

14. Modems • Dial-out configuration • Command tip and cu • Use /etc/phones and /etc/remote • Bi-directional modems • Need special treatment • Since getty normally take full control of serial ports and other processes that want to use the modem are shut out • Under HP-UX/Redhat, use a special getty called uugetty on biferectinal ports. • Uugetty shares lock file with cu, tip and uucico to avoid conflicts. Serial Devices

15. Other common I/O ports • Parallel ports • Transfer 8bits of data at once • Parallel interfaces are most commonly found on • Printer • Zip, tape drives and viedo cameras in Windows world • Two modes • EPP (Enhanced Parallel port) • ECP (Extended Capability Port) • Support DMA • Connectors and Cables • Computer usually provide a female DB-25 connector • Peripherals tend to have a female 36-pin Centronics connector • Most parallel cables are male DB-25 to male Centronics • Limited to 10 meters Serial Devices

16. Other common I/O ports • USB: The Universal Serial Bus • Features: • Makes adding peripheral devices so easy. • Standardized connectors • Hot swapping – devices can be connected and disconnected without powering down • Up to 127 devices can be connected • Legacy serial and parallel devices can be connected with adaptors. Serial Devices

17. Maximum Transfer Rates for various Connections • serial port: 115kbits/s (.115Mbits/s) • standard parallel port: 115kBYTES/s (.115MBYTES/s) • Original USB: 12Mbits/s (1.5MBYTES/s) • ECP/EPP parallel port: 3MBYTES/s • IDE: 3.3-16.7MBYTES/s • SCSI-1: 5MBYTES/s • SCSI-2 (Fast SCSI, Fast Narrow SCSI): 10MBYTES/s • Fast Wide SCSI (Wide SCSI): 20MBYTES/s • Ultra SCSI (SCSI-3, Fast-20, Ultra Narrow): 20MBYTES/s • UltraIDE: 33MBYTES/s • Wide Ultra SCSI (Fast Wide 20): 40MBYTES/s • Ultra2 SCSI: 40MBYTES/s • IEEE-1394: 100-800Mbits/s (12.5--100MBYTES/s) • Hi-Speed USB: 480Mbits/s • Wide Ultra2 SCSI: 80MBYTES/s • Ultra3 SCSI: 80MBYTES/s • Wide Ultra3 SCSI: 160MBYTES/s • FC-AL Fiber Channel: 100-400MBYTES/s Serial Devices

18. Exercise • Connect to the switch console using a straight through cable • Connect to the other Sun Blade 100’s serial console using a non modem cable Serial Devices