MAX6955 Maxim, MAX6955 Datasheet - Page 18

• Manufacturer Part Number: MAX6955
• Description: 2-Wire Interfaced / 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan
• Manufacturer: Maxim

2-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
Figure 11. Key-Scanning Configuration
Figure 12. Key-Scan Timing Diagram
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LED OUTPUT O0
LED OUTPUT O1
LED OUTPUT O2
LED OUTPUT O3
LED OUTPUT O4
LED OUTPUT O5
LED OUTPUT O6
LED OUTPUT O7
______________________________________________________________________________________
FIRST TEST OF KEY SWITCHES
A
1.6ms MULTIPLEX CYCLE 1
V
CC
12.5µs TO 187.5µs DIGIT PERIOD
LED OUTPUT O0
LED OUTPUT O1
LED OUTPUT O2
LED OUTPUT O3
LED OUTPUT O4
LED OUTPUT O5
LED OUTPUT O6
LED OUTPUT O7
KEY_A
KEY_B
KEY_C
KEY_D
IRQ
THE FIRST HALF OF A 25.6ms KEY-SCAN CYCLE
B
MICROCONTROLLER INTERRUPT
1.6ms MULTIPLEX CYCLE 2
SW A0
SW A1
SW A2
SW A3
SW A4
SW A5
SW A6
SW A7
1.6ms MULTIPLEX CYCLE 8
SW B0
SW B1
SW B2
SW B3
SW B4
SW B5
SW B6
SW B7
SECOND TEST OF KEY SWITCHES
C
1.6ms MULTIPLEX CYCLE 1
SW C0
SW C1
SW C2
SW C3
SW C4
SW C5
SW C6
SW C7
THE SECOND HALF OF A 25.6ms KEY-SCAN CYCLE
INTERRUPT ASSERTED IF REQUIRED
DEBOUNCE REGISTER UPDATED
D
SW D0
SW D1
SW D2
SW D3
SW D4
SW D5
SW D6
SW D7
1.6ms MULTIPLEX CYCLE 8
START OF NEXT KEY-SCAN CYCLE
E
A