MAX11041 Maxim, MAX11041 Datasheet - Page 8

• Manufacturer Part Number: MAX11041
• Description: The MAX11041 wired remote controller converts up to 30 different pushbuttons into an I²C register
• Manufacturer: Maxim

At power-up, the MAX11041 begins to monitor the
SENSE input for keypresses. When the MAX11041
detects a keypress at SENSE, it attempts to debounce
the SENSE input. After successful debouncing of the
input, the corresponding keypress result is inserted into
the FIFO. In addition, INT goes low to signal a keypress
to the µP.
After detecting and debouncing a key, the decoded
key is stored in one byte of the 8-word FIFO. A 7-bit
internal timer starts counting the duration of the key-
press (one count = 32ms) and the result is stored after
each increment in another byte of the 8-word FIFO. The
8th bit in the time duration byte is an overflow bit that
is set when the count reaches 128. After the count
Wired Remote Controller
Table 3. Chip ID Data Format
8
Figure 3. Reading the FIFO While the Key is Still Pressed
KEY TYPE
_______________________________________________________________________________________
V
INT
1. DEBOUNCED KEYPRESS STORED IN FIFO AND INT GOES LOW, DURATION
2. PROCESSOR READS FIFO AND INT GOES HIGH. KEY TYPE AND CURRENT
3. KEYPRESS RELEASES AND INT GOES LOW. KEY TYPE AND FINAL KEYPRESS
4. PROCESSOR READS THE FIFO AND INT GOES HIGH. KEYPRESS INFORMATION
TIMER STARTS.
KEYPRESS DURATION TIME SENT. FIFO IS NOT CLEARED.
DURATION TIME STORED IN FIFO.
STORED IN FIFO FROM STEP 3 IS CLEARED.
MAX11041
CHIP ID
Keypress Detection and Debounce
Keypress FIFO and Time Duration
➀
➁
➂
I7
0
➃
I6
TIME
TIME
0
I5
0
reaches 128, the 7-bit timer rolls over to 0 and contin-
ues to count while the 8th bit becomes set and stays
set until the associated FIFO entry is cleared. For key-
press durations longer than 8.16s, see the Extended
Keypresses section.
When the device detects another change in resistance
at SENSE (either by key release or another keypress),
the count resets and the FIFO begin recording the next
keypress/duration. This allows the 8-word FIFO to store
time duration and key-type information for up to four
keypresses and releases. When the FIFO is full and a
key is pressed, the oldest keypress information in the
FIFO is written over. Writing to the power-down bit (bit
6) in the control register or bringing SHDN low clears
the FIFO to its power-on-reset (POR) state.
Figure 4. Reading the FIFO After the Key is Released
KEY TYPE
V INT
1. DEBOUNCED KEYPRESS STORED IN FIFO AND INT GOES LOW.
2. KEYPRESS RELEASES. KEY TYPE AND KEYPRESS TIME
3. PROCESSOR READS FIFO COMPLETELY AND INT GOES HIGH.
I4
0
DURATION TIMER STARTS.
DURATION INFORMATION STORED IN FIFO.
PREVIOUS KEYPRESS INFORMATION CLEARED.
BIT NAMES
➀
I3
0
I2
0
➁
I1
0
➂
TIME
TIME
I0
0