1.nterface connector terminal assignments and signal functions
Pin number | Signal name | Signal Source | Description | ||||
2 | TXD | Printer | When using XON/XOFF | ||||
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| handshake protocol, printer |
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| transmits control code XON/XOFF |
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3 | RXD | Host | Printer receives data from host | ||||
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4 | RTS | Printer | Indicates printer current status, | ||||
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| whether the printer is Busy or |
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| Ready to receive data |
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7 | GND |
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| Signal ground |
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20 | DTR | Printer | Same as RTS (pin 4) | ||||
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b.IEEE 1284 Bidirectional Parallel Interface(Parallel Interface Specifications)
b.1) Parallel Specifications
1. | Data transmission: | Parallel |
2. | Synchronization: | Externally supplied nStrobe signals |
3. | Handshaking: | nAck and Busy signals |
4. | Signal levels: | TTL compatible |
5. | Data word length: | 8 bits |
6. | Connector (printer side): | 36 pins Centronics connector |
b.2) Parallel Interface Pin Assignments for Each Mode
Pin | Mode | Source |
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| 1 | /STB | Host | The computer presents the data on the | ||||
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| data lines, and pulses STB |
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| 2 | DATA0 | Host | Indicates the 1st data bit through 8th | ||||
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| data bit |
| 3 | DATA1 | Host |
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| 4 | DATA2 | Host |
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| 5 | DATA3 | Host |
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| 6 | DATA4 | Host |
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| 7 | DATA5 | Host |
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| 8 | DATA6 | Host |
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| 9 | DATA7 | Host |
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| 10 | nAck | Printer | Printer acknowledge signal which | ||||
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| indicates that printer has received |
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| previous data bit |
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| 11 | BUSY | Printer | Printer is busy and cannot receive | ||||
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| data |
| 12 | GND |
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| Ground |
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| 13 | Select | Printer | High electric potential | ||||
14 | 15 | NC |
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| No Connect |
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16 | 17 | GND |
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| Ground |
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| 18 | Printer | High electric potential | |||||
19 | 30 | GND |
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| Ground |
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| 31 | NC |
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| No Connect |
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| 32 | Nerror | Printer | Printer Error Signal | ||||
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| 33 | GND |
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| Ground |
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34 | 36 | NC |
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| No Connect |
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