ICS ELECTRONICS 4809A, Инструкция по эксплуатации

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The 4809A has an on-card regulator that converts unreg5.5 to +12
volt DC power to +5 Vdc to run the 4809A's circuits. A jumper on the
4809A bypasses the regulator so that the 4809A can be run from regulated
5 volt DC power.
4.3 4819A BLOCK DIAGRAM DESCRIPTION
A block diagram of the 4819A is shown in Figure 4-2. The 4819A is a
microprocessor based device that transparently passes data between the
GPIB (IEEE 488) bus and a Modbus slave device over a serial link. The
4819A also has a serial I/O connector for communicating directly with the
Modbus slave device. The 4819A is made up of seven major elements,
most of which are interconnected to the microprocessor by a common data,
address and control signal bus.
Incoming GPIB bus data and commands are received by the GPIB controller
chip. Each received character interrupts the microprocessor to place the
characters in the GPIB received data buffer. When a complete message has
been received, the parser checks the message to see if it is an IEEE-488.2
Common Command or if it is a SCPI command. SCPI commands and
IEEE-488.2 commands are parsed and used to set the 4819A's configura-
tion, perform an operation or query a parameter. Responses are placed in
the GPIB buffer so they can be returned to the host controller when the unit
is next addressed to talk.
If the message is a Modbus command then it is converted into a Modbus
packet and outputted through the serial OR gate to the Modbus device.
Incoming serial data from the Modbus slave device is converted into TTL
levels and applied to the input of the 4819A's UART. Received packets
are checked as described for the 4899A. If the received message is a valid
response, the response data is converted in to the correct format and placed
in the GPIB buffer where can be output onto the GPIB bus when the unit is
next address to talk. Messages that contain errors or Exception messages
cause the 4899A to set bits in the Questionable Register and to place an
error value in the Modbus Error Register.
The 4819A also provides a serial path from rear panel serial connector to
the Modbus device. External serial data is ORed with the serial output
of the GPIB logic to make the serial output to the Modbus device. Serial
responses from the Modbus device are routed to both the rear panel serial