Rainbow Electronics MAX7360 - Manual (Page 8)

I 2 C-Interfaced Key-Switch Controller and LED
Driver/GPIOs with Integrated ESD Protection
MAX7360
8 ______________________________________________________________________________________
Functional Block Diagram
Detailed Description
The MAX7360 is a microprocessor peripheral low-noise
key-switch controller that monitors up to 64 key switches
with optional autorepeat, and key events that are
presented in a 16-byte FIFO. The MAX7360 also features
eight open-drain GPIOs configured for digital I/O or
constant-current output for LED applications up to +14V.
The MAX7360 features an automatic sleep mode and
automatic wakeup that further reduce supply current
consumption. The MAX7360 can be configured to enter
sleep mode after a programmable time following a key
event. The FIFO content is maintained and can be read
in sleep mode. The MAX7360 does not enter autosleep
when a key is held down. The autowake feature takes
the MAX7360 out of sleep mode following a keypress
event. Enable/disable autosleep and autowake through
the configuration register (Table 8).
To prevent overloading the microprocessor with too
many interrupts, interrupt requests are issued on a
programmable number of FIFO entries, and/or after a
set period of time (Table 10). The key-switch status is
checked by reading the key-switch FIFO. A 1-byte read
access returns both the next key event in the FIFO (if
there is one) and the FIFO status. INTK functions as an
open-drain general-purpose output (GPO) capable of
driving an LED if key-switch interrupts are not required.
Up to six of the key-switch outputs function as open-
drain GPOs capable of driving additional LEDs when
the application requires fewer keys to be scanned. For
each key-switch output used as a GPO, the number of
monitored key switches reduces by eight.
Initial Power-Up
On power-up, all control registers are set to power-up
values and the MAX7360 is in sleep mode (Table 1).
128kHz
OSCILLATOR
POR
BUS
TIMEOUT
I 2 C
INTERFACE
CONTROL
REGISTERS
FIFO
KEY
SCAN
CURRENT
SOURCE
COLUMN
DRIVES
OPEN-
DRAIN
ROW
DRIVES
COLUMN ENABLE
GPO ENABLE
ROW ENABLE
CURRENT DETECT
COL0
COL1
COL2*
COL3*
COL4*
COL5*
COL6*
COL7*
PWM
GPIO
LOGIC
PORT GPIO
AND
CONSTANT-
CURRENT
LED DRIVE
LED ENABLE
GPIO ENABLE
GPIO INPUT
PORT0
PORT1
PORT2
PORT3
PORT4
PORT5
PORT6
PORT7
ROW0
ROW1
ROW2
ROW3
ROW4
ROW5
ROW6
ROW7
INTI
INTK
SDA
SCL
AD0
*GPO
MAX7360
ROTARY