Daewoo DSD-9250E, Service Manual

Page: 8 / 56

7
CIRCUIT OPERATING MANUAL
(1) Key Interface
Input can be made by Key using PIO Port for the Key I/O control.
The key value after the scanning is calculated by one Input port and 7 Output Ports.
Output ports are used with the segments of the display.
* Key Scan Method
Perform the “Low Scan”,using the Key Output Port(KO0-7) with the
cycle of 64ms. If the Key is pressed, the Key Input Port will
recognize the status as “low” eventually lead to the key code value
while going through the step from K0 to K7.
S1
R1
10K
S2 S3 S4 S5 S6 S7 S8
VCC
KI1
K0-K7
K0
K1
K2
K3
K4
K5
K6
K7
KI1
K7_SEG_CLK
K6_SEG_G K5/SEG_F K4/SEG_E K3/SEG_D K2/SEG_C K1/SEG_B K0/SEG_A
64ms
Feature 2. Key Scan