Rainbow Electronics MAX7359 - Manual (Page 7)

MAX7359
2-Wire Interfaced Low-EMI
Key Switch Controller/GPO
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PIN COL0 COL1 COL2/PORT2 COL3/PORT3 COL4/PORT4 COL5/PORT5 COL6/PORT6 COL7/PORT7
ROW0 KEY 0 KEY 8 KEY 16 KEY 24 KEY 32 KEY 40 KEY 48 KEY 56
ROW1 KEY 1 KEY 9 KEY 17 KEY 25 KEY 33 KEY 41 KEY 49 KEY 57
ROW2 KEY 2 KEY 10 KEY 18 KEY 26 KEY 34 KEY 42 KEY 50 KEY 58
ROW3 KEY 3 KEY 11 KEY 19 KEY 27 KEY 35 KEY 43 KEY 51 KEY 59
ROW4 KEY 4 KEY 12 KEY 20 KEY 28 KEY 36 KEY 44 KEY 52 KEY 60
ROW5 KEY 5 KEY 13 KEY 21 KEY 29 KEY 37 KEY 45 KEY 53 KEY 61
ROW6 KEY 6 KEY 14 KEY 22 KEY 30 KEY 38 KEY 46 KEY 54 KEY 62
ROW7 KEY 7 KEY 15 KEY 23 KEY 31 KEY 39 KEY 47 KEY 55 KEY 63
Table 1. Key-Switch Mapping
ADDRESS
CODE (hex)
READ/WRITE
POWER-UP VALUE
(hex)
REGISTER
FUNCTION
DESCRIPTION
0x00 Read only 0x3F Keys FIFO Read FIFO key scan data out
0x01 R/W 0x0A Configuration
Power down, key release enable, autowakeup, and
I
2 C timeout enable
0x02 R/W 0xFF Debounce Key debounce time setting and GPO enable
0x03 R/W 0x00 Interrupt
INT frequency setting
0x04 R/W 0xFE Ports Ports 2–7 and INT GPO control
0x05 R/W 0x00 Key repeat Delay and frequency for key repeat
0x06 R/W 0x07 Sleep Idle time to autosleep
Table 2. Register Address Map and Power-Up Condition
Key-Scan Controller
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).
Registers Description
Keys FIFO Register (0x00)
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
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).
Configuration Register (0x01)
The configuration register controls the I 2 C bus timeout
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).