4803: APPLICATION
Reading The Input Signals
The 4803 has three ways to read the digital interface lines and
input digital data as shown in Figure 2:
• Bit queries read the status of an individual bit from a specific
byte.
• Input byte commands read 8 bits of data from a specific byte.
• Strings of data can be read from multiple bytes with a data
transfer command or inputted transparently. These bytes are
preset as string input bytes by the CONFigure command. For
input strings, the 4803 reads the configured input bytes, con-
verts the data to the selected output format, and outputs it as a
string of characters. Data can be inputted with or without hand-
shaking. The input data can be formatted as decimal numbers,
as ASCII HEX characters, or into a user selected character set.
Transparent Data Transfer
The user can input and output data without using a string com-
mand by addressing the 4803 at its upper GPIB address. Data is
read from the configured input bytes each time the 4803 is addressed
to talk. The data is input and formatted just as it would be for read-
ing strings of data.
When transparently outputting data, the 4803 converts the data
and outputs it to the configured output bytes. Data can be outputted
with or without handshaking. The 4803 automatically generates a
data strobe each time it loads all of the configured output data bytes.
Multiple data words can be transmitted in the same command by
inserting a comma between data words.
Close 1,4 or Open 1,4
Short Form Command Bytes Action
Single bit is set or reset
Read 2,3 Single input line read
Eight bits are output
Value = 0001 0011
BO3 19
Eight bits are inputted
BI4?
Four nibbles or two bytes
are outputted.
Value = 0001 0010 0011 0100
PO 1234 sent to main
(lower address)
or
1234 sent to upper addr
Four nibbles or two bytes
are input
PI? query to main
(lower GPIB address)
or
data read from upper
GPIB address
Indicates a byte whose direction is set by the first command
Indicates a byte configured as an input or output byte.
Short Form Commands are shown here for brevity but the same data transfer
occurs with the equivalent SCPI Commands.
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1
2
3
4
5
6
7
8
Figure 2 4803 Digital Transfer Methods
(Figure shows 8 bytes for illustrative purposes. Actual 4803 has 5 bytes)
Input Signal Monitoring
The 4803 can monitor up to fifteen lines for signal changes and
generate an SRQ to notify the Application program when changes
occur. Monitoring is done by setting the 4803's Questionable Transi-
tion register to detect positive and/or negative signal transitions and
enabling bits in the Questionable Event register. When the enabled
bit(s) are detected, the 4803 generates an SRQ to alert the Application
to the event. The user's Application program can query the 4803's
Questionable Condition Register to determine the input signal states
and the Event Register to learn which signal changed state. Appli-
cation Bulletin 48-18 describes how to configure the 4803's Status
Reporting Structure and includes a program example.
Outputting Data
The 4803 has three ways to control the digital interface and output
data as shown in Figure 2:
• Bit commands set, reset or pulse bits in a specific byte.
• Output byte commands set all bits in a byte and latch an output
value (0 to 255) into a specific byte. Data Strobes can be manu-
ally generated if needed.
• Strings of data can be outputted to multiple bytes with a com-
mand or transferred transparently. These bytes are preset as
string output bytes by the CONFigure command. The 4803
converts the data string characters into bytes, latches the data in
the configured output bytes and generates a data strobe pulse to
update the external device. The data strings can be a series of
decimal values, ACSII HEX characters, or the 0x30-0x3F HEX
characters used in ICS's earlier interfaces.
Controlling the 4803
Figure 3 shows the 4803's configuration and data transfer com-
mands as a SCPI Command Tree. Each SCPI command has a cor-
responding Short Form command for quick programming. Most
of the functions can also be queried to verify the command setting.
(i.e. IPn? reads back the byte's polarity setting)
The ROUTe bit commands let the user set/reset and pulse indi-
vidual bits in an output byte Data Strobes can be manually generated
if needed. The PULSe commands pulse any output line as a byte,bit
value or as a channel number. A common pulse width is set by the
ROUTe:PULSe:WIDTh command. Multiple lines can be pulsed
in the same command.
SOURce Output byte commands latch an 8-bit value into a specific
output byte without pre-configuring the bytes. The SOURce string
commands let the user send strings of data to bytes that have been pre-
configured as outputs (with the CONFigure command) and generate
a data strobe with a single command. The data format is controlled
by the FORmat command. Transparent data transfer is possible in the
Dual Address Mode where bytes from the GPIB bus are formatted
and outputted to the previously configured output bytes.
SENSe bit commands read the state of a specific bit in an input
byte and SENSe byte commands read data from a specific byte.
SENSe string commands read data from bytes that have been pre-
configured as input bytes by the CONFigure command. The data
format on the GPIB bus is controlled by the FORmat command.
CALibrate Commands let the user personalize the 4803 with his
own IDN string, lock settings to prevent changes and to reset the
unit to the factory settings.
