
226
Agere Systems Inc.
T8302 Internet Protocol Telephone
Advanced RISC Machine (
ARM
)
Data Sheet
July 2001
17 Key and Lamp Controller (KLC)
(continued)
17.1.3 KLC Interrupts
The KLC will generate interrupts for key releases, key presses, and switch hook changes. The
KLC interrupt
enable register
allows the processor to enable and disable each of the three types of KLC interrupts. If an enabled
action occurs, the corresponding bits are set in the
KLC interrupt register
. Also, if the programmable interrupt
controller (PIC) enable bits are set to allow KLC interrupts to propagate to the
ARM
, the KLC interrupt bit in the PIC
will also be set. The interrupt bits will remain set until a 1 is written to the corresponding bit of the
KLC interrupt
registe
r. This action will clear the
KLC
interrupt register
bit and will remove the interrupt.
17.1.4 Timing and Reset
The KLC supports both a hardware and software reset. The software reset is accomplished by setting the
RESET
bit of the
noscan control register
to 1. The KLC will resume operation when this bit is cleared to 0. These resets
will set all LEDs to the off state and set all
control registers
to their default states. The exceptions to this are: for a
software reset, the
noscan control register
's noscan interval bits remain unchanged, as do the
interrupt regis-
ters
. The reset input will set an internal reset latch and the reset will not be removed until a valid low to high clock
transition is present.
For both types of resets, the
MSGLED
and
SPKRLED
outputs are driven low to light the
MSG
and
SPKR
LEDs
notifying the user of the reset.
The KLC will derive all of its timing from the 32.768 kHz clock provided by the real-time clock
SLOW_CLK
.
If the
source of SLOW_CLK is EXT_PROG_CLK, the value in the RTC external divider register must be 0x2C0 to
achieve proper KLC timing.
Note:
Changing the value in the RTC external divider register also changes the manner in which the RTC divider
register, and hence the RTC seconds count register, count. Thus, to achieve proper RTC timing, an external
crystal should be used.
17.2 KLC LED Drive and Key Scan Matrix Pins
The following pins are associated with the LED drive matrix and the key scan matrix:
I
Seven row-output pins
K_ROW6:0
.
I
Eight column-output pins
K_COL7:0
.
I
The signal to enable or disable current in the LED drive matrix
LCNTRL
.
I
Two outputs used to drive the speaker and message LEDs.
I
Switch hook sampling input.
.
Table 198. KLC Matrix Pins
Pin Name
LCNTRL
I/O Type
Output
Current IOH
8 mA
Current IOL
8 mA
Pull-up/Down
None
I/O Signal Description
High active output used to enable
LED drive matrix.
7 row input/output for the LED drive
matrix and key scan matrix.
K_ROW[6:0]
I/O
8 mA
8 mA
None
Low active for LED drive matrix.
High active for key scan matrix.