Service manual

2-5
2.3.1.2 Core Control Unit
The Core control unit consists of CPU, SDRAM and Flash memory.
The CPU is ADI’s DSP BF531. Its kernel running frequency is up to 400 MHz and external
frequency up to 133MHz. The kernel voltage is 0.8 V and the current consumed at 50 MHz is
as low as 26mA. The oscillating frequency of the CPU clock is 11.0592 MHz and its
expected frequency is 55MHz, which can be implemented through internal PLL frequency
multiplication. The SDRAM provides space for program running and the Flash memory
provides space for storing program, data, lingual library and configuration information. The
BF531 starts directly from the Flash memory.
2.3.1.3 Man-machine Interfaces
The functions of the buttons are listed below:
Button In measurement mode In menu mode
Audio Pause
button
Pauses audible alarms. Pauses audible alarms.
Up button Increases the beat
volume.
Moves the cursor upwards or
increases the value of selected
menu item by one.
Down button Decreases the beat
volume.
Moves the cursor downwards
or decreases the value of selected
menu item by one.
Left button Enters the main menu Enters a submenu or confirm
the selection.
Right button Locks/Unlocks buttons. Returns to the previous menu
or exits the current menu.
 LCD screen
It is a 2.4” standard QVGA (320×240) TFT LCD with a 36-pin connector. The LCD is
connected with the BF531 through a bus. 4 LEDs in series are used to backlight the
LCD. The maximum current is 15mA and driving voltage 13.2V. The main control
board provides DC power supply for the LCD and the backlight board.
 Alarm lamp
The alarm lamp gives visual alarm signals which meet applicable requirements. It
consists of 4 LEDs in parallel. The alarm LEDs receive electrical signal sent by the main
board and convert it into optical signal which is then sent to the panel through a light
conducting bar. The alarm LEDs light up in red and yellow.