MAX6954 Maxim, MAX6954 Datasheet - Page 17

• Manufacturer Part Number: MAX6954
• Description: 4-Wire Interfaced / 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan
• Manufacturer: Maxim

Figure 7. Key-Scanning Configuration
Figure 8. Key-Scan Timing Diagram
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
4-Wire Interfaced, 2.7V to 5.5V LED Display
1.6ms MULTIPLEX CYCLE 1
V
CC
12.5 s TO 187.5 s 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
______________________________________________________________________________________
Driver with I/O Expander and Key Scan
P0
P1
P2
P3
P4
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
SW C0
SW C1
SW C2
SW C3
SW C4
SW C5
SW C6
SW C7
1.6ms MULTIPLEX CYCLE 1
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
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