ICS ELECTRONICS 4863 Manual page 64

2.10 EXAMPLE DIGITAL CONNECTIONS
Figure 2-11 shows how a 4863/2363 may be used to control an external
device and input data. In this example, the external device has a small
Digital Panel Meter (DPM), a D/A converter, some control inputs, a four bit
counter, two status outputs and three LEDs. The data arrows in Figure 2-
11 show some ways that data can be transferred to/from the GPIB bus or
Serial port.
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Table 2-10 lists the signal connections for this example. The first byte is
used to input the Counter and Status signals so that they could later be
monitored by the questionable register if the need arose. The byte is directly
queried with the PORTn? query. The response format used is the one set
by the FORM:TALK command.
Bytes 2 and 3 are used to input data from a 2 1/2 Digital Panel Meter (DPM)
data as an ASCII string. The bytes are divided into two 4 bit nibbles since
each character on the GPIB bus represents only four bits on the digital
interface. The DPM's 'busy' signal is used to pulse the 4863's EDR input.
The string could be read either transparently or with the PORT? (@2,3)
query. Typical in-range responses are -199 to + 199. The Overrange signal
is wired to bit 8 of the 100s digit so Overrange responses are -999 or +999.
The polarity digit is created by wiring the Plus signal to bit 1. Bits 8, 4 and
2 are fixed with jumpers to be 101. The resulting code is 1011 for plus, 1010
for negative. In the 4863's Talk Conversion Table, character 10 is set to an
ASCII '-' and character 11 is set to an ASCII '+'.
Bytes 4 and 5 are used to output 12 bits to a D/A converter. The 4863 Strobe
line is used to load the data into the D/A's internal latch. Data transfer is
done with a string of four HEX characters, two characters per byte. Data
transfer can be as a transparent data string or can be done with the
SOURCe:DATA: VALUE command. In Figure 2-11, Byte 4 is sent as an
'0C' and Byte 5 is sent as an '4A'. The resultant output pattern is '0C4A'
Byte 6 is directly addressed with the PORTn command to output eight bits
of data. Data format can be a decimal value (0 to 255) or a hex value (#h00
to #hFF). Polarity could be set low true so a logic 1 is a low output to turn-
on the LEDs.
Tables 2-10 and 2-11 show the completed Signal Assignments and
Configuration Tables for this example.
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