W91520N Datasheet, PDF (4/16 Pages) Winbond – TONE/PULSE DIALER WITH HANDFREE AND HOLD FUNCTION

W91520N SERIES
Pin Description, continued
SYMBOL 18-PIN
HFI, HFO
-
20-PIN I/O
FUNCTION
10, 11
I, O Handfree control pins. The handfree control state is
toggled on by a low pulse on the HFI input pin. The
status of the handfree control state is described in the
following table:
CURRENT STATE
Hook SW.
HFO
Low
On Hook
High
Off Hook
High
On Hook
Off Hook
Off Hook
Low
High
NEXT STATE
Input
HFO
HFI
High
HFI
Low
HFI
Low
Off Hook Low
On Hook Low
On Hook High
Dialing
Yes
No
Yes
Yes
No
Yes
HFI pin is pulled to VDD by an internal resistor.
Detailed timing diagrams are shown in Figure 3.
BLOCK DIAGRAM
XT XT
SYSTEM CLOCK
GENERATOR
HKS
HFI
ROW
(R1 to R4, Vx)
COLUMN
(C1 to C4)
KEYBOARD
INTERFACE
DTMF
D/A
CONVERTER
READ/WRITE
COUNTER
CONTROL
LOGIC
LOCATION
LATCH
RAM
PULSE
CONTROL
LOGIC
ROW & COLUMN
PROGRAMMABLE
COUNTER
DATA LATCH
& DECODER
MODE
H/P MUTE
T/P MUTE
DP/C5
HFO
-4-