CPI CMP 200 Series Service Manual page 291

7
Theory of Operation
7.2.9 DAP (MD-0938)
The DAP circuits consist of switching circuits to control the outputs at J4, and circuits to feed the DAP
pulses back to the CPU. Data latch U19 and driver U20 switch the +5 V and +15 V supplies via Q2, Q3,
and Q1 as required to control and test the DAP chamber. For DAP chambers with differential outputs,
JW14 is jumpered from pins 2-3, thus connecting the differential output from the DAP chamber directly to
the input of U1. For DAP chambers with a single-ended output, JW14 must be jumpered from pins 2-1.
This connects the output of the DAP chamber to the input of opto-coupler U94. This provides increased
noise immunity for single-ended DAP chambers, as the signal must be greater than approximately 2 V in
order to turn on the opto-coupler. The single-ended output of U94 is then connected to the input of U1.
The RS-485 driver, U1, sends single-ended (not differential) pulses to the CPU via U78. The DAP pulses
are counted by, and the related calculations are performed by the generator CPU.
7.2.10 Temp sensor / programming jumpers (MD-0925)
The inverter temperature sensor is mounted on a thermal sensor board that is mounted on one of the
inverter heat sinks. The output of the inverter temperature sensor is connected to J17-2 on the generator
control board. The temperature sensor, which has an output of 10mV / °C, is connected to the input of
U79A. The output of U79A is scaled 100mV / °C; this is divided by R162 / R163 to bring the signal within
the useable range of A to D converter U45. The digital output of U45 is read by the generator CPU, which
will inhibit further exposures if it calculates that the next exposure will exceed a safe inverter temperature.
MD-0925 also shows programming jumpers JW12, JW2, and JW13. JW12 tells the CPU if the generator
has a cooling fan. JW-12 should be jumpered from pins 2-3 for generators with fans, and pins 1-2 if a
new-style generator control board is used to upgrade or repair older generators without fans. Note that if
the jumper is in position 1-2 (no fan), the generator duty cycle will be reduced.
JW2 is used to upgrade the generator firmware. This is set to JW2 pins 1-2 for normal operation, and pins
2-3 to upgrade the firmware. JW13 is factory-set, and should not be reconfigured in the field.
7.2.11 Serial communications (MD-0937)
When the generator is switched on and the start-up diagnostics are finished, the console will attempt to
communicate with the generator. The console will send data to the generator, and then wait for a
response from the generator. If the console receives a response, communication may continue. If the
console CPU does not receive a response from the generator CPU, a communication error message will
be displayed.
When the membrane console is sending data to the generator, DS2 on the console board will flash. DS3
on the generator control board will flash when data is being received by the generator control board from
the membrane console or the touchscreen console. DS2 on the generator control board and DS3 on the
membrane console board (if applicable) will flash to indicate that the generator control board is sending
data to the console.
U11 on the console board (membrane consoles) is a RS-232 driver, and converts the +5 V TTL levels
from the CPU to RS-232 levels for the serial port, J4. DS5 and DS4 on the console board will flash to
indicate that data is being sent to, and received from the serial port.
The generator control board includes two serial communications ports. These include J21, which is an
RS-232 communications port, and J22, which is used for optional features. The generator control board
also includes USB port J1 and associated circuits.
DS1 on the console board (membrane consoles) and on the generator control board will flash at a
consistent 1 Hz rate if the related CPU is operational.
Use and disclosure is subject to the restrictions on the title page of this CPI document.
Page 7-10
®
CMP 200 X-Ray Generator Service Manual
CPI Canada Inc.
Ch # 901476-09 Rev. C