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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 Definitions of Request Bits in IEEE 1284 Communication Mode
Xflag
bit Definition Bit Values
（76543210）Hex Code When
Supported
In the
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
2
Request Device ID：Return Data Using
Nibble ModeRev Channel Transfer
Byte Mode Rev Channel Transfer
ECP Mode Transfer without RLE
ECP Mode Transfer with RLE
00000100
00000101
00010100
00110100
04H
05H
14H
34H
High
High
High
High
High
High
Low
Low
1 Reserve 00000010 02H High Low
O Byte Mode Reverse Channel Transfer 00000001 01H High High
non Nibble Mode Reverse Channel Transfer 00000000 00H Low Low
Illegal or Contradictory Request Other than
above
Other than
above -- Low
The printer only supports the Nibble and Byte modes. For a request for any other mode, Xflag is set to Low.