Citizen CT-S2000 Command Reference Manual page 173

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 Definition
7 Request Extensibility Link
6 Request EPP Mode
5 Request ECP Mode with RLE
4 Request ECP Mode
3 Reserved
Request Device ID: Return Data Using
Nibble Mode Rev Channel Transfer
2 Byte Mode Rev Channel Transfer
ECP Mode Transfer without RLE
ECP Mode Transfer with RLE
1 Reserved
0 Byte Mode Reverse Channel Transfer
Nibble Mode
None
Transfer
Illegal or Contradictory Request
The printer only supports the Nibble and Byte modes. For a request for any other mode, Xflag is set to Low.
Reverse Channel
Bit Values
Hex. Code
(76543210)
10000000
01000000
00110000
00010000
00001000
00000100
00000101
00010100
00110100
00000010
00000001
00000000
Other than
above
- 171 -
Xflag
When
Supported
80H High
40H High
30H High
10H High
08H High
04H High
05H High
14H High
34H High
02H High
01H High
00H Low
Other
than
—
above
In the
Printer
Low
Low
Low
Low
Low
High
High
Low
Low
Low
High
Low
Low