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Using the Serial (RS-232) Interface
8-5
IM 755601-01E
8
XON-RS
Data transmission control
Software handshaking is performed between the instrument and the PC. When an X-
OFF code is received while sending data to the PC, the instrument stops the data
transmission. When it receives the next X-ON code, it resumes the data transmission.
CS signal from the PC is ignored.
Data reception control
Hardware handshaking is performed between the instrument and the PC. When the free
area of the receive buffer decreases to 64 bytes, the instrument sets “RS=False.” When
the free area increases to 192 bytes, it sets “RS=True.”
CS-RS
Data transmission control
Hardware handshaking is performed between the instrument and the PC. When the CS
signal becomes False while sending data to the PC, the instrument stops the data
transmission. When the CS signal becomes True, it resumes the data transmission. X-
OFF is treated as data.
Data reception control
Hardware handshaking is performed between the instrument and the PC. When the free
area of the receive buffer decreases to 64 bytes, the instrument sets “RS=False.” When
the free area increases to 192 bytes, it sets “RS=True.”
Precautions to be taken with respect to Data Reception Control
When handshaking is used to control the data reception, additional data may be received
even when the free area drops below 64 bytes. If the receive buffer becomes full, all
overflow data are discarded regardless of the handshaking control. When the free area
becomes available again, it will be able to store data once again.
256 bytes
Used
64 bytes free
When handshaking is used, the instrument
signals the PC to stop when data in the buffer
cannot be processed fast enough and the
free area drops to 64 bytes.
Used
192 bytes free
After the data reception is stopped as
described above, data in the buffer continues
to be passed to the internal program. When
the free area increases to 192 bytes, it
resumes data reception.
Used
If the buffer becomes full in spite of the
handshaking control, all overflow data are
discarded.
Data Reception Control using Handshaking
Note
The program on the PC must be designed so that the receive buffers on the instrument and the
PC do not become FULL.
8.3 Handshaking