EM91420 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
FUNCTIONAL BLOCK DIAGRAM
RMUTE
SDO HFO HDO
COL1
COL2
COL3
COL4/KT
COL5
XMUTE
Row/Column
programming counter
Keyboard
interface
(column)
Output circuit
Memory
(Melody)
XIN
XOUT
Oscillator
latch
&
decoder
D/A
converter
DTMF
Timing/Control circuit
ROW1
ROW2
ROW3
ROW4
VDD
HFI
HKS
DRING
VDD
Keyboard
interface
(Row)
Input circuit
Pulse
generator
PO
PIN DESCRIPTIONS
Symbol
ROW1~ROW4
Function
Keyboard scan pins of row group. In idle state (HKS is “High” and HFO is “Low”),
these pins stay “High impedance” level to prevent power consumption. Otherwise,
these pins switch to “High” level for detecting keyboard entry. These pins will output
600 Hz signal while keyboard is scanning.
Keyboard scan pins of column group. In idle state, these pins stay “High impedance”
level. Otherwise these pins switch to “Low” level for detecting keyboard entry. These
pins will output 600 Hz signal while keyboard is scanning.
The fourth column group pin of the keyboard that also provides the keytone output
. Normally, this pin stays “Low” level for detecting keyboard entry. After a valid
keyboard entry, this pin will output keying confirmation tone that is 600 Hz signal and
30 ms duration. To prevent signal interference, while DTMF issue, it will disable key
tone output except function key.
Oscillator input and output pins. A 3.579545 MHz crystal or ceramic resonator must
be crossed connection to XIN and XOUT pins which generate system clock.
The Tone/Pulse MUTE signal output pin that is NMOS open-drain output structure.
This pin will switch to “Low” level during Tone/Pulse dialing and hold function .
Otherwise, this pin stays “High impedance” level.
Positive and negative power supply input pins. Recommended operating voltage from
2.0Vdc to 5.5Vdc.
Handfree inputs pin which accepts falling edge signal to turn “on” or turn “off”
handfree function. This pin is hysteresis input structure and built-in pull up resistor
(typically 200 Kohms).
Handfree outputs pin that is designed to control telephone line for on-hook dialing or
control speakerphone circuit for handfree conversation. When handfree function is
executed, this pin will switch to“High”. Otherwise, this pin stays “Low” level.
The DTMF (Dual Tone Multi-Frequency) and music signals output pin. Normally,
this pin stays “Low” level. In Tone dialing mode, this pin will output DTMF signal
that is corresponding to keyboard 0 .. 9, * and # keys. Beside this, in the line hold
duration, this pin will issue dual-tone music for telephone line.
10.1.1997
3
COL1~COL3 and COL5
COL4/KT
XIN and XOUT
XMUTE
V
DD
and V
SS
HFI
HFO
DTMF
* This specification are subject to be changed without notice.
EMC [ ELAN MICROELECTRONICS CORP ]
