13.2.3 Precautions
1)The Negotiation phase is triggered when the IEEE 1284 Active signal sent by the host becomes High.
2)In Compatibility mode, the time when the negotiation process begins is, as a general rule, after the host sets nStrobe to High and then the printer outputs an nAck pulse.
Once the nStrobe signal is set to High, however, the printer immediately moves into the Negotiation phase when the high state of IEEE 1284 Active is detected, even if the nAck pulse has yet to be output or is being output. In this case, if the printer has returned to Compatibility mode after Termination, no nAck pulse will be output.
3)Negotiations can be entered from the Busy or Error state of the Compatibility mode. In this case, the printer will not return to the Busy or Error state before the negotiations, but still remains in the printer state just after Termination.
4)If the host requested a communication mode that is not supported by the printer, it must move into the Termination phase and return to the Compatibility mode.
Table 2.4.1 Definitions of Request Bits in IEEE 1284 Communication Mode
|
| Bit Values |
| Xflag | ||
Bit |
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| ||
Definition | Hex. | When | In the | |||
(76543210) | ||||||
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|
| supported | printer | ||
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| |||
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| |
7 | Request Extensibility Link | 10000000 | 80H | High | Low | |
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| |
6 | Request EPP Mode | 01000000 | 40H | High | Low | |
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|
| |
5 | Request ECP Mode with RLE | 00110000 | 30H | High | Low | |
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| |
4 | Request ECP Mode | 00010000 | 10H | High | Low | |
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| |
3 | Reserve | 00001000 | 08H | High | Low | |
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|
| |
| Request Device ID: Return Data Using |
|
|
|
| |
| Nibble Mode Rev Channel Transfer | 00000100 | 04H | High | High | |
2 | Byte Mode Rev Channel Transfer | 00000101 | 05H | High | High | |
| ECP Mode Transfer without RLE | 00010100 | 14H | High | Low | |
| ECP Mode Transfer with RLE | 00110100 | 34H | High | Low | |
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| |
1 | Reserve | 00000010 | 02H | High | Low | |
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| |
0 | Byte Mode Reverse Channel Transfer | 00000001 | 01H | High | High | |
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None | Nibble Mode Reverse Channel Transfer | 00000000 | 00H | Low | Low | |
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| |
| Illegal or Contradictory Request | Other than | Other than | — | Low | |
| above | above | ||||
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| |||
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| |
Note: The printer only supports the Nibble and Byte modes. For a request for any other mode, Xflag is set to Low.
