Samsung S5PC100 User Manual page 1747

S5PC100 USER'S MANUAL (REV1.0)
5 KEYPAD SCANNING PROCEDURE
At initial state, all column lines (outputs) are low level. But column data output tri-state enable bits are all high,
therefore, if the tri-state enable mode is not used, these bits should be written to zeros. If no key pressed state, all
row lines (inputs) are high (used pull-up pads). If any key is pressed, the corresponding row and column lines are
shorted together and a low level is driven on the corresponding row line, generating a keypad interrupt. The CPU
(software) writes with a LOW level on one column line and HIGH on the others to the KEYIFCOL register. Each
write time, the CPU reads the value of the KEYIFROW register and detects if one key of the corresponding
column line is pressed. When the scanning procedure is end, the pressed key (one or more) can be detected.
S5PC100X
SCAN_X[7:0]
SCAN_Y[7:0]
0 8 16 24 32 40
1 9 17 25 33 41
2 10 18 26 34 42
3 11 19 27 35 43
4 12 20 28 36 44
5 13 21 29 37 45
6 14 22 30 38 46
7 15 23 31 39 47
Figure 10.8-3 Keypad Scanning Procedure I
input : pull-up (PAD
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or external)
S5PC100X
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50 58
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SCAN_X[7:0]
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SCAN_Y[7:0]
KEYPAD INTERFACE
0 8 16 24 32 40
1 9 17 25 33 41
2 10 18 26 34 42
3 11 19 27 35 43
4 12 20 28 36 44
5 13 21 29 37 45
6 14 22 30 38 46
7 15 23 31 39 47
output : external blocking
resistor for avoiding short
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49 57
50 58
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54 62
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10.8-3