
W91540N SERIES
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Pin Description, continued
SYMBOL
MODE
18-PIN
13
20-PIN
15
I/O
I
FUNCTION
Pulling mode pin to V
SS
places dialer in tone
mode.
Pulling mode pin to V
DD
places dialer in pulse
mode with M/B ratio of 40:60 (10 ppS, except for
W91542N/542AN is 20 ppS).
Leaving mode pin floating places dialer in pulse
mode with M/B ratio of 33.3:66.7 (10 ppS, except
for W91542N/542AN is 20 ppS).
HKS
10
12
I
The
HKS
(hook switch) input is used to sense
whether the handset is on-hook or off-hook.
On-hook state,
HKS
= 1: chip is in sleeping
mode, no operation.
Off-hook state,
HKS
= 0: chip is enabled for
normal operation.
HKS
pin is pulled to V
DD
by an internal resistor.
The key tone output is a conventional CMOS
inverter. The key tone is generated when any
valid key is pressed; the KT pin generates a 1.2
KHz square wave at 35 mS. When no key is
pressed, the KT pin remains in low state.
The function of this terminal is to prevent "0"
dialing and "9" dialing under PABX system long
distance call control. When the first key input
after reset is 0 or 9, all key inputs, including the 0
or 9 key, become invalid and the chip generates
no output. The telephone is reinitialized by a
reset.
KT
5
(except for
W91541LN)
5
(except for
W91541ALN)
O
LOCK
5
(only for
W91541LN)
5
(only for
W91541ALN)
I
The function of the
LOCK
pin is shown below:
N-channel open drain dialing pulse output.
Flash key will cause DP to be active in either
tone mode or pulse mode.
LOCK PIN
FUNCTION
V
DD
V
SS
Floating
"0", "9" dialing inhibited
Normal dialing
"0" dialing inhibited
DP
/
C5
11
13
O
In lock mode, DP remains low for 300 mS during
off-hook delay time.
The timing diagram for pulse mode is shown in
Figure 1(a, b, c, d).