uba2051t NXP Semiconductors, uba2051t Datasheet - Page 23

• Manufacturer Part Number: uba2051t
• Description: Uba2050 A ; Uba2051 A;c One-chip Telephone Ics With Speech, Dialler And Ringer Functions
• Manufacturer: NXP Semiconductors

Philips Semiconductors
K
The pins are directly connected to a traditional single
contact keyboard. The keyboard is normally static with
outputs R1 to R4 at LOW level and inputs C1 to C4 with
internal pull-up resistors. When any key is pressed,
scanning is done to detect which key has been pressed.
A second key entry will be valid after having released the
first key entry. Simultaneously pressing several keys will
result in no action.
2000 May 19
handbook, full pagewidth
EYBOARD DETECTOR
One-chip telephone ICs with speech,
dialler and ringer functions
t
t
dd
rd
= release debounce time.
= depress debounce time.
(
PINS
C1
key entry
key valid
TO
C4
AND
Fig.24 Timing diagram debouncing.
R1
TO
t dd
R4)
23
A key entry becomes valid when the depress debounce
time t
valid key, the scanning is frozen when the release
debounce time t
The pins R1 to R4 are LOW and pull-down resistors
replace pull-up resistors at pins C1 to C4 when
V
DD
< V
dd
has elapsed (see Fig.24). After the release of a
POR
UBA2050(A); UBA2051(A;C)
.
rd
t rd
has elapsed.
MGM341
Product specification