MAX7359 Maxim, MAX7359 Datasheet - Page 7

• Manufacturer Part Number: MAX7359
• Description: The MAX7359 I²C interfaced peripheral provides microprocessors with management of up to 64 key switches
• Manufacturer: Maxim

Key inputs are scanned statically, not dynamically, to
ensure low-EMI operation. As inputs only toggle in
response to switch changes, the key matrix can be
routed closer to sensitive circuit nodes.
The key controller debounces and maintains a FIFO of
key-press and release events (including autorepeated
key presses, if autorepeat is enabled). Table 1 shows
keys order.
_____________________Initial Power-Up
On power-up, all control registers are set to power-up
values and the MAX7359 is in sleep mode (Table 2).
The keys FIFO register contains the information pertain-
ing to the status of the keys FIFO, as well as the key
events that have been debounced (Table 3). Bits D0 to
Table 1. Key-Switch Mapping
Table 2. Register Address Map and Power-Up Condition
CODE (hex)
ROW0
ROW1
ROW2
ROW3
ROW4
ROW5
ROW6
ROW7
ADDRESS
PIN
0x00
0x01
0x02
0x03
0x04
0x05
0x06
KEY 0
KEY 1
KEY 2
KEY 3
KEY 4
KEY 5
KEY 6
KEY 7
COL0
_______________________________________________________________________________________
READ/WRITE
Read only
R/W
R/W
R/W
R/W
R/W
R/W
Registers Description
Keys FIFO Register (0x00)
KEY 10
KEY 11
KEY 12
KEY 13
KEY 14
KEY 15
KEY 8
KEY 9
COL1
Key-Scan Controller
POWER-UP VALUE
COL2/PORT2 COL3/PORT3 COL4/PORT4 COL5/PORT5 COL6/PORT6 COL7/PORT7
(hex)
0x3F
0x0A
0xFF
0x00
0xFE
0x00
0x07
KEY 16
KEY 17
KEY 18
KEY 19
KEY 20
KEY 21
KEY 22
KEY 23
Key Switch Controller/GPO
2-Wire Interfaced Low-EMI
KEY 24
KEY 25
KEY 26
KEY 27
KEY 28
KEY 29
KEY 30
KEY 31
Configuration
FUNCTION
REGISTER
Key repeat
Keys FIFO
Debounce
Interrupt
Sleep
Ports
D5 denote which of the 64 keys have been debounced
and the keys are numbered as in Table 1.
D7 indicates if there is more data in the FIFO except
when D5:D0 indicate key 63 or key 62. When D5:D0
indicate key 63 or key 62, the host should read one
more time to determine whether there is more data in
FIFO. It is better to use key 62 and key 63 for rarely
used keys. D6 indicates if it is a key-press or release
event except when D5:D0 indicate key 63 or key 62.
Reading the key-scan FIFO clears the interrupt INT
depending on the setting of bit D5 in the configuration
register (0x01).
The configuration register controls the I
feature, enables key release detection, enables autowake,
and determines how INT should be deasserted. By writing
to bit D7, you can put the MAX7359 into sleep mode or
operating mode, however, autosleep and autowake,
when enabled, also change the status of this bit (Table 4).
KEY 32
KEY 33
KEY 34
KEY 35
KEY 36
KEY 37
KEY 38
KEY 39
Power down, key release enable, autowakeup, and
I
INT frequency setting
Read FIFO key scan data out
Key debounce time setting and GPO enable
Ports 2–7 and INT GPO control
Delay and frequency for key repeat
Idle time to autosleep
2
C timeout enable
KEY 40
KEY 41
KEY 42
KEY 43
KEY 44
KEY 45
KEY 46
KEY 47
Configuration Register (0x01)
DESCRIPTION
KEY 48
KEY 49
KEY 50
KEY 51
KEY 52
KEY 53
KEY 54
KEY 55
2
C bus timeout
KEY 56
KEY 57
KEY 58
KEY 59
KEY 60
KEY 61
KEY 62
KEY 63
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