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At power up, U56 outputs /RESET/ and /HALT/ signals to the microprocessor - the microprocessor does not
execute the software instructions when both lines are low. Pressing the Reset Switch SW5 provides the same
reset when the system is already on. After approximately 200ms, these lines goes high, the microprocessor
begins to execute the software instructions stored in the EPROM U63.
U56 will also drive the /RESET/ line low if the 5 VDC supply voltage falls below
|4.65 VDC. The /RESET/
signal is used to reset the following chips:
Multifunction Programmable Timer U47
All EPLDs U39, U40, U49 and U62
System Dual UART U42
Lamp Volts Frequency Generator U45
Lamp Energy Frequency Generator U46
Test DAC U32
Servo controller U50
U52 and U53 provide 2K of 16 bit nonvolatile read/write memory to the microprocessor. System energy
calibration and error factors stored in the NVRAM will be maintained even when power is removed.
U63 is a four megabit PROM (programmable, read-only memory). Software instructions are permanently
stored on this chip. Software upgrades can be accomplished by replacing the PROM.
NOTE: Consult Section 6 (Parts List) for a list of P/N’s for the software versions currnet at the release
of this manual.
U57 and U58 provide 32K of 16 byte of RAM. The microprocessor uses the RAM to keep track of
miscellaneous values while the system is turned on. Data stored in RAM is lost when the system is turned off.
Inputs from the vendor supplied DC power supply provide the Controller PCB with +5 VDC, ± 15 VDC, and
+24 VDC through J1, as shown in the upper left corner of 8-5.
LED31 serves as an address strobe indicator for the microprocessor. LED31 is a dual package which displays
an orange color under normal operation of the microprocessor. As U62 asserts an address strobe signal
(/AS/) to the microprocessor, it will also output /BAS/ and BAS signals to LED31. As both signals turn on
and off, LED31 oscillates producing an orange color. If the microprocessor or any of its associated circuits
malfunction, LED31 stops oscillating adn either a red or green color is exhibited.
The Programmable timer U47 (Refer to 8-5) provides timing functions for the main processor, including the
following:
1MSTIMER - At 1 millisecond intervals an interrupt request is asserted by the timer. The main pro-
cessor uses this interrupt to increment/decrement various registers used to time events.
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