Keithley 7707, User Manual

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32-bit input pattern (double-word)
For remote programming, there is a single command to read a 32-bit pattern (double-word) formed by four input ports.
Thirty-two bits of data (two words) is called a double-word. The following command reads a double-word bit pattern:
SENS:DIG[:DATA]:WORD? <clist>
The only valid channels for the double-word <clist> parameter is 13.
This command is used to read channel 11. Channel 11 is combined with channels 12, 13, and 14 to form a 32-bit pattern. When
channel 11 is read as a double-word, Bit 0 (B0) of channel 11 will be the LSB, and Bit 7 (B31) of channel 14 will be the MSB.
The bit pattern can be returned as a decimal, binary, hexadecimal, or octal value. Figure 18 provides decimal weighting for
each bit. The binary equivalent of the returned bit pattern value directly identifies the state of each line (bit). For example,
assume the following binary equivalent of a returned 32-bit pattern:
00001111 11111111 11111111 11110000
The above bit pattern indicates that lines (bits) B4 through B27 are TTL high (logic ‘1’). The other bits are TTL low
(logic ‘0’).
The :FORMat command sets the retuned reading format for the bit pattern. For details on commands to read bit patterns, see
“
Reading digital inputs — Remote programming,” page 32 .
Reading digital inputs
Before reading a digital input pattern, an I/O channel must first be set as an input port. This can be done from the front panel or
remote programming.
From the front panel, each 8-bit port is read individually. For remote programming, commands are provided to read 8-bit
patterns (bytes), 16-bit patterns (words), and a 32-bit pattern (double-word).
Front panel basic operation
From the front panel, the decimal, hexadecimal, or octal equivalent of the 8-bit pattern can be read for each input port. The
digital data format and port type (input or output) are set from the CONFIG option of the CARD menu. For details on using the
CARD menu, see “CARD menu”.
There are two ways to read digital input ports from the front panel. You can use the CLOSE key to select a channel to read or
scroll through channels using the VIEW option of the CARD menu.
Setting digital data format
The CONFIG option of the CARD menu is used to set the digital data format. The menu is accessed by pressing SHIFT and
then CARD. After selecting the CONFIG option and the slot that has the Model 7707, select one of the formats.
FORMAT: ASC Decimal format
FORMAT: HEX Hexadecimal format
FORMAT: OCT Octal format
FORMAT: BIN Binary format. Note that there is not enough room on the display for a binary reading.
Therefore, the hexadecimal format will instead be used to display digital input readings.