2070LX Controller – User Manual 47
Version 1.0
This line is normally forced to High state through a 10K pull-up resistor to Vcc; it is connected to the
driver’s input of a RS-485 transceiver whose differential outputs are connected to the enable pins of the
RS-485 transceiver that handle the SP-4 communication; while the driver’s input is high, the enable inputs
disable the SP-4 communications and the C50 enable signal goes to high, this signal is one of the
differential outputs and it is routed to P3 connector.
Bell
It is an electronic bell controlled by the microcontroller used to signal receipt of ^G (hex 07) and RESET
condition. It is performed by a buzzer which is managed by the microcontroller applying a 2 KHz square
signal for a period of 350mS.
AUX Switch
This is a toggle switch that forces the status of the STOPTIME line from microcontroller to Low by
connecting a pull-up to logic ground. The microcontroller receives the status of this line and sends a code
to the CPU through the P3 connector; this information is used according to the application running in
CPU.
RESET Switch
It is a push-button switch located on the back of the FPA on the PCB sub-assembly. It serves as switch
that once touched it momentary pulls down a line monitored by the microcontroller which then reset the
operation and also sends a reset the LCD through the P2 connector.
ACTIVE LED
An LED with a series resistor connected to Vcc is activated by the CPU through the P3 connector. This
LED is normally used to indicate the status of the application running in the CPU.
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