Fresenius Medical Care 4008 E Technical Manual page 357

DIP switch arrays
Two eight-fold switch arrays permit various operating parameters to be predefined.
Status indicator LEDs
During the program run, an eight-fold LED line can be used for the indication of status values.
After the machine has been switched on, various system initializations are performed by the
program. Altogether, this procedure is performed four times, if the system is correctly initialized.
Subsequently, the CRC check and the RAM test are performed. In addition to the text on the
alphanumeric display, various LEDs are turned on. After these tests have also been completed
successfully, the light-emitting diodes are used for indicating interrupt events and their proces-
sing time during the further course of operation.
Multifunction PAL
A programmable logic module PAL16V8 or GAL16V8 is provided for decoding the chip-select
signals and for various logical operations for various components of the CPU 1 board.
Boolean operation tables and logical equations filed in the PAL determine the behavior of the
outputs in relation with the input signals.
By the use of a PAL, it was possible to reduce the number of the integrated logic ICs to a large
extent.
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Fresenius Medical Care 4008 4/09.03 (TM)