11-3
IM CW120-E
Communication Functions
11
11.1 RS-232
● Allowable Combinations of Handshaking Methods
To assure data exchange via the RS-232 interface with a computer, both
devices must follow a predetermined procedure (may be decided between
both parties) by sending/receiving a series of electric signals. This series
of exchanged signals is called a handshake. The handshake to be used
may vary depending on the computer connected but must match the
handshake performed by the computer. The following types of
handshakes are possible with the CW120/121.
OFF/OFF
XON/XON
XON/RS
CS/RS
Quits
Transmission
upon Receipt
of X-off;
Restarts
Transmission
upon Receipt
of X-on
Quits T
ransmission
When CB
(CTS)
Becomes
False; Restarts
Transmission
When It
Becomes True
No
Handshake
No
Handshake
Transmission Control
(Control of Data Transmission to Computer)
Reception Control
(Control of Data Reception to Computer)
Sends X-off
When Data in
Reception
Buffer Has
Reached 3
Quarters of the
Capacity;
Sends X-on
When Data in
Reception
Buffer Has
Decreased to a
Quarter of the
Capacity
Resets CA
(RTS) to False
When Data in
Reception
Buffer Has
Reached 3
Quarters of the
Capacity; Sets
CA (RTS) to
Tr ue When
Data in
Reception
Buffer Has
Decreased to
a Quarter of the
Capacity
Handshaking
Method
Possible Combinations of Handshaking Methods
Software
Handshake
Hardware
Handshake
Software
Handshake
Hardware
Handshake
When Selecting OFF/OFF
• Transmission Control
No handshake is performed between the CW120/121 and computer. The
CW120/121 handles the X-off and X-on codes from the computer as data
and ignores CTS (CS in JIS).
• Reception Control
No handshake is performed between the CW120/121 and computer.
After the reception buffer inside the CW120/121 becomes full, the
overflowed data will be discarded. RTS (RS in JIS) is always true.
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