Datasheet
Rev. 1.10 16 May 16, 2011 Rev. 1.10 17 May 16, 2011
HT16K33
RAM Mapping 16*8 LED Controller Driver with keyscan
Keyscan
●
The keyscan logic uses one, two or three of the KS0, KS1and KS2 logic outputs. An interrupt
output that flags a key press is optional. The INT flag can be read (polled) through the serial
interface, allowing INT/ROW15 to be used as a general purpose logic output or as a ROW open-
drain driver.
●
One small-signal diode is required per key switch when more than one key is connected to KS0,
KS1 or KS2. The diodes prevent two simultaneous key switch depressions from shorting the
COM drivers together. For example, if SW1 and SW14 were pressed together and the diodes
were not tted, COM1/KS0 and COM2/KS1 would be shorted together and the LED multiplexing
would be incorrect.
●
The keyscanning circuit utilises the COM1/KS0 to COM3/KS2 outputs high as the keyscan output
drivers. The outputs COM0 to COM7 pulse low sequentially as the displays are multiplexed. The
actual low time varies from 64μs to 1024μs due to pulse width modulation from 1/16th to 16/16th
for dimming control. The LED drive mode waveforms and scanning shows the typical situation
when all eight LED cathode drivers are used.
●
The maximum of thirty-nine keys can only be scanned if the scan-limit register is set to scan the
maximum KS0 to KS2.
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The keyscan cycle loops continuously over time, with all thirty-nine keys experiencing a full
keyscanning debounce over 20ms. A key press is debounced and an interrupt issued if at least one
key that was not pressed in a previous cycle is found to be pressed during both sampling periods.
●
The keyscan circuit detects any combination of keys pressed during each debounce cycle (n-key
rollover).
●
The INT output is active-low when the “act” bit of row/int set register is set to “0”.
●
The INT output is active-high when the “act” bit of row/int set register is set to “1”.
COM1/KS0
COM2/KS1
COM3/KS2
SEG3/K1
SEG4/K2
SEG5/K3
SEG6/K4
SEG7/K5
SEG8/K6
SEG9/K7
SEG10/K8
SEG11/K9
SEG12/K10
SEG14/K12
SEG15/K13
SEG13/K11
=
SW1
SW14
SW27
SW2 SW3 SW4 SW5 SW6 SW7 SW8 SW9 SW10 SW11 SW12 SW13
SW15 SW16 SW17 SW18 SW19 SW20 SW21 SW22 SW23 SW24 SW25 SW26
SW28 SW29 SW30 SW31 SW32 SW33 SW34 SW35 SW36 SW37 SW38 SW39