ADP5588
display the unlock message. The host then reads the lock status
register to see if the keypad is unlocked. After the first key event
interrupt, the state machine does not interrupt the processor
again unless the correct sequence is keyed. The state machine
resets if the correct sequences are not keyed before the keypad
lock interrupt mask timer expires.
Autoincrement
The ADP5588 features automatic increment during I2C read
access. This allows the user to increment the address pointer
without having to send a read command for subsequent
addresses. This minimizes processor intervention and, therefore,
saves processor bandwidth and current drain. Bit 7 of Register 0x01
must be set to initiate autoincrement (see Figure 16 for the full
write and read sequence).
The state of the keypad lock interrupt mask bit (Register 0x01,
Bit 2) in the configuration register determines whether the
interrupt pin is asserted when the keylock interrupt status bit
(Register 0x02, Bit 2) is set. Setting the keylock interrupt mask
Key Event Interrupt
On a key event (KE) interrupt, the processor reads the interrupt
register to determine the cause of the interrupt. If the KE_INT
bit in Register 0x02 is the cause of the interrupt, the state
machine sets the KE_INT bit and reads the key event count
from the KEC[3:0] field in Register 0x03 to determine the number
of events. It then reads the INT_STAT register (Register 0x02)
to make sure that no new events have come in. After all the
events are read, the KEC field is decremented to zero (KEC =0)
and the KE_INT bit can be cleared by writing a 1 to it. Both key
presses and key releases are capable of generating key event
INT
bit causes the
pin to be asserted when the keylock interrupt
status bit is set in Register 0x02; clearing that bit masks the
interrupt, causing the interrupt pin not to respond to the keylock
interrupt status bit. The mask interrupt timer should be set for
the time that it takes for the LCD to dim or turn off so that, if a
key is pressed, the backlight is set to bright mode again or reset
to turn on the LCD.
When the unlock mask interrupt timer equals 0, only the
correct unlock sequence can generate an interrupt. Disabling
the unlock mask interrupt timer allows the processor to remain
undisturbed for situations in which the user has the phone in a
pocket or purse and the keys are constantly pressed. The flow
chart in Figure 6 shows the interaction of the interrupt mask
timer and interrupt generation.
INT
interrupts. The KE_INT bit cannot be cleared, and the
pin
cannot be deasserted, until the FIFO is cleared of all events.
REG. 0x1D
THROUGH 0x1F
KP_MODE
REG. 0x02
WRITE 1 TO CLEAR
KE_INT
REG. 0x01
KE_IEN
GENERAL-PURPOSE INPUTS AND OUTPUTS
INT DRIVE
AND
REG. 0x03
The ADP5588 supports up to 18 programmable GPIOs that can
be configured to address a variety of uses. Figure 7 shows the
makeup of a typical GPIO block where GPIOx represents any of
the 18 I/O lines.
READ KE(s) TO CLEAR
KEC
Figure 6. Key Event Interrupt Generation
Keypad Lock/Unlock Feature
V
CC
The ADP5588 has a locking feature that allows the user to lock
the keypad or GPIs (configured to be part of the event table).
Once enabled, the keypad lock can prevent generation of key
event interrupts and key events to be recorded in the key event
table. This feature comprises the Unlock Key 1 and Unlock Key 2
registers (Register 0x0F and Register 0x10), the keypad lock
interrupt mask, the keypad unlock timers (Register 0x0E),
and the LCK1 and LCK2 bits, and the keylock enable bit
(Register 0x03).
Dx_PULL
Dx_IN_DBNC
Dx_IN
DEBOUNCE
V
CC
GPIOx
Dx_OUT
Dx_DIR
The unlock keys can be programmed with any value of the keys
in the keypad matrix or any GPI values that are part of the key
event table. When the keypad lock interrupt mask timer is
enabled, the user must press two specific keys before a keylock
interrupt is generated or keypad events are recorded. After the
keypad is locked (set Bit 6, Register 0x03 to enable the lock), the
first time that the user presses any key, a key event interrupt is
generated. No additional interrupt is generated unless both
unlock key sequences are correct; then a keylock interrupt is
generated.
Figure 7. Typical GPIO Block
General Purpose Inputs (GPI)
The ADP5588 allows the user to configure all or some of its
GPIOs into GPIs (general-purpose inputs). After the GPIOs are
configured as GPIs, the user can opt to also turn on pull-up
resistors and interrupt generation capability, thus reducing the
amount of software monitoring and processor interaction and
saving power.
If the correct unlock keys are not pressed before the mask timer
expires, the state machine starts over. The first key event
interrupt is generated to allow the software to see that the user
has pressed a key so that the host can turn on the LCD and
The programmed level of the GPI interrupt determines the
active level of the GPI pin. For example, if a GPI interrupt level
Rev. A | Page 9 of 28
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