Appendixes
73
5. RS-232C protocol
(1) X-ON/X-OFF system (see figure)
This is a control system in which the data transmitting request signal (X-ON (11H) code) and the
data transmitting stop signal (X-OFF (13H) code) are output.
Requirements of output of X-ON code:
• When the power is switched to ON.
• When the receive buffer has less than 2K bytes available, the X-OFF code is output, and the
receive buffer has at least 4K bytes available.
Requirements of output of X-OFF code:
• When the receive buffer has less than 2K bytes available.
Buffer in use
Note: Even if each code is ready for output, the same code will not be transmitted twice
successively (except when the power is turned on or the printer is reset from the control
panel).
(2) Ready/Busy system (see figure)
This is a control system in which the DTR is output at Ready (High) or Busy (Low) level. The DTR,
however, is always output at Ready (High) level except the following:
Requirements of output of DTR ‘Low’:
• When the receive buffer has less than 2K bytes available. When this condition is detected, the
printer keeps a ‘Low’ level until the receive buffer has at least 4K bytes available.
Receive buffer size = 32K bytes
4K bytes
2K bytes
Receiving data
-ON code output
-OFF code output
2 Specifications
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