Seiko FB-900 - Manual (Page 173)

Any of four handshaking protocols is selected in the
extended setup mode.
- DTR protocol
- X-ON/X-OFF (I) protocol
- X-ON/X-OFF (II) protocol
- ETX/ACK protocol
Control of these serial protocols is based on the free area in the data
buffer. There are two protocol control points based on the data buffer:
CIN, where the ready state changes to the busy state, and CRN, where
the busy state changes to the ready state. The values of these points are
shown below.
When 512KB or 8KB buffer size is selected,
CIN: 1KB
CRN: 2KB
When 128-byte buffer size is selected,
CIN: 32 bytes
CRN: 64 bytes
When the free space in the data buffer is reduced below the CIN value,
the printer enter the busy state and remains there until the free space
exceeds the CRN value. When the free space exceeds the CRN value,
the printer enters the ready state.
In this protocol, the printer state is indicated by the SRTS signal
(pin No. 11) and DTR signal (pin No. 20).
When the printer is ready, each signal goes ON (+12 V). When
the printer is busy or in the offline state, each signal goes OFF
(-12 V).
When the printer is busy or in the offline state, the computer does
not send data.
However, data from the computer can be received when the
printer is busy or in the offline state.
(1) When the power is turned on,
The SRTS and DTR signals go ready when data input is
enabled on completion of initialization after turning on
the power.
● Serial interface
7-8 — 7. Interface specifications —
Handshaking protocol
See page 3-49.
DTR (READY/BUSY) Protocol