MAX7348AEP Maxim Integrated, MAX7348AEP Datasheet - Page 14

• Manufacturer Part Number: MAX7348AEP
• Description: Peripheral Drivers & Components - PCIs Low-EMI Key Switch & Sounder Controller
• Manufacturer: Maxim Integrated

Eight key-scan registers are described in the following
sections.
The keys FIFO register contains the information pertain-
ing to the status of the keys FIFO, as well as the key-
press events that have been debounced (Table 8). Bits
D0 to D5 denote which of the 64 keys have been
debounced and the keys are numbered as in Table 2
and Figure 1. D6 indicates whether the present
debounced key is the last one in the FIFO, with 1
denoting that there are more keys after the present one,
and 0 denoting that the present debounced key is the
last one stored in the FIFO. D7 is the overflow flag,
which denotes whether the keys FIFO has overflowed.
Reading the key-scan FIFO clears the interrupt INT. INT
is only reasserted after the FIFO has been emptied by
performing enough read operations.
2-Wire Interfaced Low-EMI Key Switch
and Sounder Controllers
Table 9. Debounce Register Format
14
Debounce time is 9ms
Debounce time is 10ms
Debounce time is 11ms
Debounce time is 12ms
All the way through to
Debounce time is 37ms
Debounce time is 38ms
Debounce time is 39ms
Debounce time is 40ms
GPO ports disabled (full key-scan functionality)
GPO port 7 enabled
GPO ports 7 and 6 enabled
GPO ports 7, 6, and 5 enabled
GPO ports 7, 6, 5, and 4 enabled
GPO ports 7, 6, 5, 4, and 3 enabled
GPO ports 7, 6, 5, 4, 3, and 2 enabled
Power-up default setting
______________________________________________________________________________________
DEBOUNCE REGISTER
REGISTER
Key-Scan Registers
Keys FIFO Register
ADDRESS CODE
(hex)
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
The debounce register sets the time for each debounce
cycle, as well as setting whether the GPO ports are
enabled or disabled. Bits D0 through D4 set the
debounce time in increments of 1ms starting at 9ms
and ending at 40ms (Table 9). Bits D5 through D7 set
which one of the GPO ports is to be enabled. Note that
not any port can be enabled at a particular time. The
GPO ports can be enabled only in the combinations
shown in Table 9, from all disabled to all enabled.
The autorepeat register sets the autorepeat frequency
(repeat rate) and its delay. The autorepeat function allows
a key to be consecutively asserted when the key itself is
pressed down without being released. The autorepeat
delay specifies the delay between the first press and the
beginning of the autorepeating, provided that the key has
not been released. The autorepeat frequency specifies
how fast the continuously pressed-down key to be assert-
ed once autorepeating has started is. Bits D0 through D3
specify the autorepeat delay in terms of debounce cycles
PORTS ENABLE
D7
X
X
X
X
X
X
X
X
X
0
0
0
0
1
1
1
1
D6
X
X
X
X
X
X
X
X
X
0
0
1
1
0
0
1
1
D5
X
X
X
X
X
X
X
X
X
X
0
1
0
1
0
1
1
REGISTER DATA
D4
—
0
0
0
0
1
1
1
1
X
X
X
X
X
X
X
1
DEBOUNCE TIME
Autorepeat Register
D3
—
0
0
0
0
1
1
1
1
X
X
X
X
X
X
X
1
Debounce Register
D2
—
X
X
X
X
X
X
X
0
0
0
0
1
1
1
1
1
D1
—
0
0
1
1
0
0
1
1
X
X
X
X
X
X
X
1
D0
—
0
1
0
1
0
1
0
1
X
X
X
X
X
X
X
1