7.10.2 Waveform Data in 16-bit Format
This format is only possible if the Waveform Processing option is
installed. The 9400A must be set to this format with the command
COMM FORMAT. In this format, raw data, i.e. 8-bit ADC output, are
represented in the most significant byte. The least significant byte
consists of 8 bits of zeros. The unsigned 16-bit data values in the
range 0 - 65535 are transformed into volts as follows:
V = gain * ((data - 32768)/8192 - (offset - 200)/25) * 200/(vgain
The terms are identical to those of Section 7.10.1, except that the
factors of the first expression are multiplied by 256.
7.11 Use of the Service Request (SRQ) Interrupts
A Service Request (SRQ) is generated whenever the RQS bit of the Main
Status Byte (STB i) becomes 1. The user must demask the condition bits
of interest in order to allow the generation of SRQ, e.g., to make the
9400A generate an interrupt upon the occurrence of an overload in
either channel I or 2:
MASK 4,6
Sets the mask of the INTERNAL STATE byte (STB 4) to the
binary value 00000110, i.e. it demasks the 2 overload bits.
If an overload occurs, the mask now allows the propagation of
the bit to the INTERNAL STATE CHANGE bit of the Main Status
Byte (STB I).
MASK 1,8 Sets the mask of the Main Status Byte (STB I) to the binary
value 00001000, i.e. it demasks the bit INTERNAL STATE
CHANGE. This now allows the propagation of this bit to the
RQS bit of STB i. Note that the R0S bit need not be demasked;
it always generates an SRQ when set.
7.11.1 Service Request in GPIB
The Service Request (SRQ) is a dedicated interrupt line on the GPIB
bus. The handling of this interrupt is the responsibility of the user’s
GPIB driver on the host computer. The driver may allow the linking of a
user-written service routine to the interrupt. The GPIB protocol allows
an alternative way of reading the Main Status Byte (STB I) through the
Serial Poll. The execution of the serial poll is again a GPIB driver
routine on the host computer. Normally, the value of STBI is identical,
whether it is read by Serial Poll or with the explicit read command
"STB i,?". A difference occurs, however, when more than one condition
occurs that may set the RqS-bit:
Remote Operations
7-52
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