ST3917B 查看數據表（PDF） - STMicroelectronics
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ST3917B Datasheet PDF : 16 Pages
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ST3917A - ST3917B
PIN CONNECTIONS
C1
1
C2
2
C3
3
SEL
4
OSC
5
PULSE
6
MODE/PT
7
HKS
8
GND
9
RXOUT
10
GRX
11
RXIN
12
IREF
13
VCC
14
28
R1
27
R2
26
R3
25
R4
24
MU/MFI
23
VDD
22
GDTMF
21
MIC+
20
MIC-
19
GTX
18
REG
17
LN
16
ILINE
15
LED
PIN DESCRIPTION
Figure 1 : Keyboard Configuration
123
456
789
*0 #
Flas h
Tone /P ulse
Pause
LND
C1, C2, C3, R4, R3, R2, R1
(Keyboard inputs, Pins 1, 2, 3, 25, 26, 27, 28)
The device interfaces with either the standard 2 of
8 with negative common or the single contact
(Form A) keyboard. Column 4 of the keypad is
connecting to ground.
A valid keypad entry is either a single Row con-
nected to a single Column or GND simultaneously
presented to both a single Row and a single Col-
umn. In its quiescent or standby state, during nor-
mal off-hook operation, the Rows are initialized at
logic level 1 (VDD) and the columns are initialized
at logic level 0 (GND). Pulling any row input low
enables the on chip oscillator. Keyboard scanning
then begins.
Scanning consists of Rows and Columns alter-
nately switching high through on chip pullups. After
both a Row and Column keys have been detected,
the debounce counter is enabled and any noise
(bouncing contacts, etc) is ignored for a debounce
period (TKD) of 32ms. At this time, the keyboard is
sampled and if both the Row and Column informa-
tion are valid, the information is buffered into the
LND location.
In the tone mode, if two or more keys in the same
row or if two or more keys in the same column are
depressed a single tone will be output. The tone
will correspond to the common row or common
column for which the two keys were pushed. This
feature is for test purposes, and single tone will not
be redialed. Also in the tone mode, the output tone
is continuous in the manual dialing as long as the
key is pushed. The output tone duration follows the
Table 1. When redialing in the tone mode, each
DTMF output is 90ms duration, and the tone sepa-
ration (inter signal delay) is 90ms.
Table 1 : Output Tone Duration
Key Push Time, T
Tone Output
T < 32ms
No output, ignored by the device
32ms < T < 90ms + Tkd 90ms duration
T > 90 ms + Tkd Output duration = T - tkd
2/16
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