APX 525/625 Generator Revision C Diagnostics
©
2005 Del Medical Imaging Corporation
7/5/2005 Page 175
Theory of Operation
Communications scheme: (See illustration X1 for overview)
The human-machine interface between the operator and the APX 525/625 generator
takes place at the operator’s console.
The Console Display Board provides visible selection data to the operator through
the Liquid Crystal Display. The operator selects from the available technique
options, using the membrane keyboard on the face of the operator’s console.
Keyboard entries are input to the CPU Board (124-5045G1), and the results are
updated and displayed on the LCD.
The Interface Board communicates bi-directionally through a parallel interface from
connector J1 to connector J2 on the CPU board (124-50451).
Selected technique parameters are sent from the CPU Board to the Data Board
(124-0101G1) through an isolated asynchronous serial data link. The APX 525/625
serial communications scheme utilizes a 64-bit word, followed by a blank period,
which is continually updated and repeated as long as the generator is energized.
The serial data stream is received and decoded at the Data board, creating two
clock signals, which are used to clock the serial data through the shift registers (data
clock) on the data board, the mAs Regulator Board (124-0145G1), and the AEC
Main Board (124-0126G1) and then to latch the received data in parallel format
(memory clock).
Twenty-four of the bits of Parallel data are used to feed several D/A converters that
develop reference voltages for kV, Filament Preheat, and mA. Four more of the bits
are used to decode the Prep and Expose requests from the operator’s console,
thirteen bits are used to load mAs data, and the remainder are used for various
selections, such as Buckys, focal spots, commutation capacitor relays, and other
accessories, such as photo timing and Tomo devices.
Return communication from the generator to the operator’s console is accomplished
with a serial data link, as well as hardwired lines for mAs pulses, x-ray backup
status, and exposure duration. Fault conditions, such as kV and Filament Overload
faults, are decoded from the serial data.
All other board to board communications are accomplished via direct connections on
the motherboard and from there to the Power Supply, I/O Board, and Relay Control
Board, using a combination of wire harnesses and edge connectors.
Control of kV, mA, and Filament Preheat levels begins with analog reference
voltages, decoded by D/A converters on the Data Board (124-0101G1), which are
then sent out to the kV Regulator and mA/Rotor Boards.
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