╔════════════════════════ ═══════════════════ ═══════════════════╗ ║ Iron. ║ ╙─────────────────────────────── ───────────────────────────────╜ (R) EVP-SOFT Connecting a printer with a Centronics interface to the LPT port. Connecting the cable to the parallel interface adapter is carried out through a 25-pin connector type D-shell (DB-25), and with printer side uses a special 36-pin connector type Centronics. Since the frequency of transmitted signals can reach tens of kilohertz, the length of such cables usually does not exceed rises three meters. Distribution of signals across the contacts of both connectors are shown in Tables 1 and 2. Generally speaking, for simple transferring data to the printer does not require all signals that define divided by the Centronics standard. In order to ensure operation of the interface, it is enough to use 8 bits of data data (D0-D7), data strobe and busy signal printer (Busy). Now a few words about those signals that rye are commonly used. Data Strobe. When the computersends data to the printer, it within 5 µs should activate this signal (low level Ven). This printer is notified that the data is ready according to appropriate tires. Data D0 - D7. Data is transmitted via these 8 signal lines from computer to printer. After the Data Strobe signal is established the printer reads the information. Acknowledge. If the printer accepted the values set by the computer data, then in confirmation it is within approximately 10 µs keeps this line active (low level). Busy. If the printer cannot receive data, then the signal is activated is changing (high level). This can happen, for example, following the following cases: when initializing the printer, if the printer prints symbol, is in the OFF-LINE or PAUSE state, when it appears internal error or when the end of paper is detected. Paper out. This signal (high level) tells the computer about running out of paper. If you insert a new one into the printer sheet, the signal is deactivated (low level). Select. Using this signal, the printer tells the computer ru that it is selected and active. Umany Select printers have constant value (high level) or does not use at all - Xia. Auto feed. Activation of this signal (low level) causes advances the paper one line forward in the printer. Usually it can be fixed at one of two DIP switch levels chatel. As a rule, the transition to another line is carried out programmatically - by outputting certain codes to the port. Error. This signal from the printer can be active (low level) in the following situations: if the printer is in OFF-LINE or PAUSE if you run out of paper or while printing There was an error in the chat. Init. If the signal on this line is active (low level), ven) within approximately 50-100 μs, then the initiation occurs The printer's implementation is the same as when it is turned on. In this case, The print buffer is also cleared. Select Input. Activation (low level) and deactivation The application of this signal is similar to the supply of control codes DC1 (De- vice Control 1) - select device and DCЗ - cancel selection devices. Ground. This is the "Body" ("Ground") signal for signalsdata and control signals. Table 1. Parallel signals Table 2. Parallel signals interface (DB-25 connector) interface (Centronics connector on a computer) on a printer) ╔═════╤════════╤════════════╗ ╔═════╤════════╤══════════════╗ ║Cont.│Direction│Signal ║ ║Cont.│Direction│Signal ║ ╠═════╪════════╪════════════╣ ╠═════╪════════╪══════════════╣ ║ 1 │ Output │Data Strobe ║ ║ 1 │ Input │Data Storbe ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 2 │ Output │Data 0 ║ ║ 2 │ Input │Data 0 ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 3 │ Output │Data 1 ║ ║ 3 │ Input │Data 1 ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 4 │ Output │Data 2 ║ ║ 4 │ Input │Data 2 ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 5 │ Output │Data 3 ║ ║ 5 │ Input │Data 3 ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 6 │ Output │Data 4 ║ ║ 6 │ Input │Data 4 ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 7 │ Output │Data 5 ║ ║ 7 │ Input │Data 5 ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 8 │ Output │Data 6 ║ ║ 8 │ Input │Data 6 ║╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 9 │ Output │Data 7 ║ ║ 9 │ Input │Data 7 ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 10 │ Input │Acknowledge ║ ║ 10 │ Output │Acknowledge ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 11 │ Input │Busy ║ ║ 11 │ Output │Busy ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 12 │ Input │Paper Out ║ ║ 12 │ Output │Paper Out ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 13 │ Input │Select ║ ║ 13 │ Output │Select ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 14 │ Exit │Auto feed ║ ║ 14 │ Input │Auto feed ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 15 │ Input │Error ║ ║ 15 │ - │No connect ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 16 │ Exit │Init ║ ║ 16 │ - │Ground ║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║ 17 │ Output │Select Input║ ║ 17 │ - │Chassis Ground║ ╟─────┼────────┼────────────╢ ╟─────┼────────┼──────────────╢ ║18-25│ - │Ground ║ ║ 18 │ - │+5V ║ ╚═════╧════════╧════════════╝ ╟─────┼────────┼──────────────╢ ║19-30│ - │Ground ║╟─────┼────────┼──────────────╢ ║ 31 │ Input │Init ║ ╟─────┼────────┼──────────────╢ ║ 32 │ Exit │Error ║ ╟─────┼────────┼──────────────╢ ║ 33 │ - │Ground ║ ╟─────┼────────┼──────────────╢ ║ 34 │ - │Clock ║ ╟─────┼────────┼──────────────╢ ║ 35 │ Login │Test ║ ╟─────┼────────┼──────────────╢ ║ 36 │ Input │Select Input ║ ╚═════╧════════╧══════════════╝
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