Tektronix 2714, Руководство программиста

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Introduction to Programming
2714 & 2715 Programmer Manual
1–7
Setting the Number of Data Bits. Item 2 of the RS-232 PORT CONFIGURATION
Menu, DATA BITS, selects the number of data bits sent per character. This is
either seven or eight. Eight bits must be selected for binary transfers. Press [2] on
the KEYPAD to choose between seven or eight data bits.
Setting Parity. Item 3 of the RS-232 PORT CONFIGURATION Menu, PARITY,
determines whether odd or even parity is used for data checking, or it selects no
parity checking. The default setting is NONE. To change the PARITY selection,
repeatedly press [3] on the KEYPAD until ODD, EVEN, or NONE is displayed.
Setting the Message Terminator. Item 4 of the RS-232 PORT CONFIGURATION
Menu, EOL, selects the EOL (end-of-line) indicator used to terminate messages
sent over the spectrum analyzer’s RS-232 interface. The terminator can be CR
(carriage return, ASCII 13), LF (line feed, ASCII 10), or CR LF (carriage return
followed by line feed). To change the EOL status selection, repeatedly press [4]
on the KEYPAD until CR, LF, or CRLF is displayed.
When a controller sends data, the spectrum analyzer interprets either CR or LF as
a terminator, independent of the setting.
Selecting a Data Flow Control Method.
Item 5 of the RS-232 PORT CONFIGU-
RATION Menu, FLOW CONTROL, selects between three flow control
methods: SOFT, HARD, or NONE. An explanation of each selection follows.
SOFT: When the spectrum analyzer sends data through the interface and SOFT
flow control is enabled, CTRL-S (ASCII 19, same as pressing [CTRL] and [S]
simultaneously) halts the data stream until CTRL-Q (ASCII 17) is received. Any
other character received in the interim is ignored. This type of flow control can
be used with a 3-wire setup because additional handshake lines are not needed.
When SOFT control is selected, the spectrum analyzer sends CTRL-S when its
input data buffer is within 200 characters of being full. It sends CTRL-Q when
the buffer empties to the point at which additional characters can be safely
accepted (less than 200 characters remain in the buffer). If the input buffer is
allowed to overflow, the spectrum analyzer discards the incoming data and
signals an error (Event 372).
HARD: When HARD flow control is selected, the instrument sends data as long
as the CTS (Clear-To-Send) line is TRUE and stops sending data if CTS goes
FALSE. Additional handshake lines (more than a 3-wire RS-232 implementa-
tion) are required to support HARD flow control.
When receiving data and HARD flow control is selected, the spectrum analyzer
asserts RTS (Request-To-Send) TRUE until the input buffer is within 200
characters of being full. It then sets RTS FALSE. Data is received while RTS is
FALSE until the buffer overflows. If the buffer is allowed to overflow, the
spectrum analyzer signals an error (Event 372), and incoming data is discarded.