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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
Xflag
Bit Definition
Bit Values
Hex. When In the
(76543210)
supported
printer
7 Request Extensibility Link 10000000 80H High Low
6 Request EPP Mode 01000000 40H High Low
5 Request ECP Mode with RLE 00110000 30H High Low
4 Request ECP Mode 00010000 10H High Low
3 Reserve 00001000 08H High Low
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
1 Reserve 00000010 02H High Low
0 Byte Mode Reverse Channel Transfer 00000001 01H High High
None Nibble Mode Reverse Channel Transfer 00000000 00H Low Low
Illegal or Contradictory Request
Other than Other than
— Low
above above
Note: The printer only supports the Nibble and Byte modes. For a request for any
other mode, Xflag is set to Low.