MAX7349AEG-T Maxim Integrated, MAX7349AEG-T Datasheet - Page 15

• Manufacturer Part Number: MAX7349AEG-T
• Description: Peripheral Drivers & Components - PCIs Low-EMI Key Switch & Sounder Controller
• Manufacturer: Maxim Integrated

ranging from 8 debounce cycles to 128 debounce cycles
(Table 10). Bits D4 through D6 specify the autorepeat
rate or frequency ranging from 4 to 32 debounce cycles.
Bit D7 specifies whether the auto-repeat function is
enabled with 0 denoting autorepeat disabled and 1
denoting autorepeat enabled.
The interrupt register contains information related to the
settings of the interrupt request function, as well as the
status of the INT output, which can also be configured
as a GPO. Bits D0 through D4 set the key-scan interrupt
frequency. By setting bits D0 through D4 to an appropri-
ate value, the interrupt can be asserted at the end of the
selected number of debounce cycles (Table 11). This
number ranges from 1 to 31 debounce cycles. If bits D0
through D4 are set to 00000, the INT output is config-
ured as a GPO that is controlled by bit D6 in the ports
register and the INT output is not asserted. However, the
INT status bits D5, D6, and D7 are still set and cleared in
the normal way at the end of each debounce cycle as if
bits D0 through D4 were set to 00001.
Bits D5 and D6 denote whether an interrupt was set
due to a key-scan event (bit D5) or to an alert event (bit
D6). Bit D7 represents whether an interrupt request has
been asserted with 0 denoting no INT asserted and 1
denoting that INT has been asserted.
The interrupt register is a read-only register and writes
to it are ignored. Reading the interrupt register does
clear an alert event INT, but does not clear a key-scan
event INT. An interrupt request caused by a key-scan
event(s) is cleared when the FIFO is emptied.
The configuration register reflects the sounder status,
controls the I
input interrupt feature, enables the sounder to respond
to both alert input and key debounce events, and con-
trols the shutdown of the device (Table 12).
The ports register sets the values of ports 2 through 7 and
the INT port when configured as GPOs. The settings in
this register are ignored for ports not configured as
GPOs, and a read from this register returns the values
stored in the register and not the actual port conditions
(Table 13). The ports register also serves to read the alert
input and this is done through bit D0 with a 0 denoting a
low on the alert input and a 1 denoting a high.
The key-sound register specifies the duration and fre-
quency of the sound to be executed by the sounder con-
troller when a key or a set of keys are debounced if the
2
C bus timeout feature, enables the alert
______________________________________________________________________________________
2-Wire Interfaced Low-EMI Key Switch
Configuration Register
Key-Sound Register
Interrupt Register
Ports Register
and Sounder Controllers
sounder output has been enabled to be set by a key
debounce event in the configuration register. When this
happens, the information of bits D7 through D1 is passed
on to the sounder register and the appropriate sound is
executed (Tables 14, 16). Least significant bit D0 is
ignored and always set to 1 when transferred to the
sounder register. See Table 16 for the format of setting
the frequency and duration of the sound to be executed.
If a key-sound register command is sent as 000xxxx
(continuous), then the command is stored as 111xxxx
(1000ms) in the sounder register.
The alert sound register specifies the duration and fre-
quency of the sound to be executed by the sounder con-
troller at the falling edge of the alert input if the sounder
output has been enabled to be set by the alert input in
the configuration register. If this is the case, the informa-
tion of bits D7 through D1 is passed on to the sounder
register and the appropriate sound is executed (Tables
15, 16). Least significant bit D0 is always set to 1 and
this value is ignored when transferred to the sounder
register. See Table 16 for the proper format of setting the
frequency and duration of the sound to be executed.
Note that if an alert sound register command is sent as
000xxxx (continuous), then the command is actually
stored as 111xxxx (1000ms) in the sounder register.
The sounder register stores the frequencies and duration
of the sounds to be executed by the sounder, as well as
the state of its two-deep FIFO (Table 16). D0 denotes
whether another command is lined in the queue at any
given moment. A 0 in D0 denotes that the queue is empty
while a 1 denotes that there is another command. By writ-
ing 0 to D0, the present command is executed and the
queue is cleared. When sending a command that has a
D0 set to 1, the queue is checked and, if empty, the sent
command is added to it while, if full, the sent command
replaces the queued command.
Bits D0 and D1, when taken in conjunction, set the level
of the sounder output when configured as a GPO and
also control the autoloop function provided that the rest of
the bits (D7 through D2) are set to 0. When the sounder is
configured as a GPO, the levels of the output are set by
D1, a 0 denoting a low and a 1 denoting a high. When D0
is set to 1 and the rest of the bits are set to 0, D1 controls
the autoloop function as defined in Table 16.
Bits D7 through D1 control the frequency and duration of
the sounds to be executed by the sounder. These sounds
include the musical notes of the 5th octave plus some
notes from the 6th and 7th octaves as well. See Table 16.
Alert Sound Register
Sounder Register
15