F.W. Bell 7030, Инструкция по эксплуатации

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F.W. BELL Model 7030 Gauss/Tesla Meter Instruction Manual
7-4 Section 7 – Remote Operation
RS-232
FUNCTIONAL
DESCRIPTION
(Continued) Data is transmitted to the instrument on the receive (RX) line. Data is
transmitted to the computer on the transmit (TX) line. In most cases these
are the only signals needed for communications.
However, there may be a need to control the flow of data between the
instrument and the computer. For example, if the computer is receiving
data from the instrument but is interrupted by another task, it may want to
halt the instrument’s transmission until it has completed that task. This can
be accomplished in one of two ways.
Hardware Handshaking
Two lines called Clear-To-Send (CTS) and Request-To-Send (RTS) are
used to control the flow of data. This is often referred to as “hardware
handshaking”. The instrument will not transmit data until the computer
asserts the CTS line. Likewise the computer should not transmit data until
the instrument asserts the RTS line.
Hardware handshaking can be enabled or disabled from the
COMMUNICATIONS menu. It must also be enabled or disabled on the
computer.
Software Handshaking
Another way to control the flow of data is called “software handshaking”. In
this method two special characters are used to halt or resume the flow of
data. The XOFF character is decimal 19 (hex 13). If the instrument
receives the XOFF character at any time it will halt transmission until it
receives the XON character, which is decimal 17 (hex 11). Likewise if the
instrument transmits an XOFF character to the computer the computer
should halt transmission until it receives the XON character.
Software handshaking can be enabled or disabled from the
COMMUNICATIONS menu. It must also be enabled or disabled on the
computer. If disabled the instrument will treat the XON and XOFF
characters as any other character.
Figure 7-2 RS-232 Connector