Fukuda Denshi HR-800, Service Manual

Page: 31 / 70

Circuit Explanation
Serial Communication
The communication with the main body of the monitor is serial communication of 500kbps, and it
communicates (transmit and receive) according to a strong differential signal against foreign
noises.
Membrane Key Input
The key input is detected by causing the pull-up signal short circuit to GND by the membrane key.
To prevent chattering,a CR circuit is connected.
Motor Drive
Utilizes DC motor IC of H bridge, and by just inputting a control pulse, the motor can be driven.
Memory
SRAM: 128kbye x 8bit
FIFO: 63byte
EEPROM: 2kbit
SHCPU
Internal (
Ｉ
φ ) 64 MHz
Bus (B φ ) 32 MHz
Peripheral (
Ｐ
φ ) 16 MHz
System Clock
Utilizes 8MHz crystal oscillator output as CPU system clock.
Buzzer
Activates the buzzer with 4KHz frequency clock.
PLD
The motor activation and strobe output timing is controlled inside the PLD.
Speed: 25mm/s, 50mm/s
Strobe Width: Adjustable Range 0 to 1000
μ s (Resolution 50 μ s)
Temperature Detection by the Software
Overheat (“OVH”) will be detected when 80
℃
is exceeded, and stops the printing and motor
activation. Once the “OVH” is detected, printing and motor activation will not resume until the
temperature drops below 60
℃
.
Temperature Detection by the Hardware
Monitors the temperature of 100
℃
and above by the comparator, and if it is detected for 3ms or
more, stops the +24V supply to the printhead and +18V supply to the +24V output DC-DC
converter.
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