- 135 -
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
(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 Reserved
00001000
08H
High
Low
2
Request Device ID: Return Data Using
Nibble Mode Rev 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 Reserved
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
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.
