Epson TM-U950P - B/W Dot-matrix Printer Specification page 149

1) Host Requests Reverse Transfer.
2) Successful Negotiation to Another mode.
3) Peripheral Has Data To Send.
4) Peripheral Has No Data To Send.
5) Host Goes To Idle.
6) Peripheral Has New Data.
7) Peripheral Has Data Send.
8) Host Requests Data Byte.
9) Host Receives Data Byte.
Peripheral Has No More Data To Send.nDataAvail = High
10) Host receives Data Byte.
Peripheral Has More Data.
11) Host requests termination.
12) Interface Returns To The Compatible Mode.
*In states other than in the process of data acception, the interface is set in the Forward
Idle phase.
J.1.2.1 Phases in Compatibility Mode
• Compatibility Mode Forward Data Transfer phase:
• Compatibility Mode Forward Idle phase:
J.1.2.2 Phases in Nibble Mode and Byte Mode
• Reverse Data Transfer phase:
• Reverse Host Busy Data Available phase:
• Reverse Host Busy Data Not Available phase:
• Reverse Idle phase:
• Reverse Interrupt phase:
nDataAvail = Low
nDataAvail = High
HostBusy = Low
nDataAvail = Low
This phase allows the printer to accept data from the host. The host
and the printer perform handshaking in response to the signals,
nStrobe, nAck and Busy. The host shall not initiate any negotiation
phase to a new operating mode until the interface successfully returns
to the Compatibility Mode Forward Idle phase.
The interface is in Compatibility Mode, with no data transfer in
progress. The host is allowed to initiate a data transfer in
Compatibility Mode, or initiate negotiation phase to a new operating
mode.
Data transfer from the printer to the host.
The printer has data to transmit to the host.
The printer has no more data to transmit.
No data transfer is in progress and the host is waiting for the printer
data. When any printer data is available, the printer will cause the
interface to go to the Reverse Interrupt phase.
This phase makes the printer report to the host that it has got data to
transfer in the Reverse Idle phase. While in this phase, the host
may cause the interface to go to the Termination phase.