Fanuc C-Executer Operating Manual
B-62443EN-3/03E
- 771 -
(2) Receiving handshake
DC code is used to request the source device to stop or restart sending data
according to the state of receiving buffer.
Send DC1 : request to restart sending data
Send DC3 : request to stop sending data
These DC1 or DC3 codes are automatically transmitted by the serial
communication driver.
[5] Communication mode
Application program can select one of the three communication modes,
"transmit only", "receive only", and "transmit and receive"
(1) Transmit only mode
Only data transmission from application program to external device can take
place in this mode. Application program cannot use library functions for
receiving data. Data received from external device are ignored except DC
codes.
(2) Receive only mode
Only data transmission from external device to application program can take
place in this mode. Application program cannot use library functions for
sending data. All received data from external devices are passed to
application program.
(3) Transmit and receive mode
Both data sending and receiving can take place in this mode. Application
program can use all serial library functions. Received data code from external
device is interpreted as follows in accordance with the selected flow control
mode.
(a) "DC code flow ctrl" is ON for transmission
DC codes included in the receiving data from external device are interpreted
as flow control characters and they are not passed to the application program.
(b) "DC code flow ctrl" is OFF for transmission
Because external device would not send DC codes to the application program
for flow control purposes in this mode, all receiving data including DC codes
are passed to the application program.
In this mode, care should be taken for the relationship between flow control
method and transmitted data. When bi-directional "DC code flow ctrl" is
employed, DC codes in transmitted data, if included as data, cannot be
discriminated from flow control DC characters. And these data not only are
blocked to pass to the application program but cause flow control failure.
Moreover, the DC code to announce "send stop/send restart" cannot be sent to
the destination, if "send data" is inhibited by the hardware signal. For these
reasons, only text data should be transmitted when "DC code flow ctrl" is
employed. If hardware signal handshake is employed, there is no restriction
in the code of transmitted data.