EMC EM91421 Series User manual

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
1
* This specification are subject to be changed without notice. 10.1.1997
GENERAL DESCRIPTION
The EM91421 is a series of tone/pulse switchable dialers that is composed of T/P dialer and T/P dialer with
20-set memories. The EM91421 series provide necessary functions of telephone set for application in any
environment, such as Pulse dialing, Tone (DTMF) dialing, Handfree dialing, keying tone ,and lock functions.
The lock function is designed to inhibit toll dialing operation. Beside this, melody generator, ring detector and
SDO (Serial Data Output) functions are provided in advance version. Melody generator will output dual-tone
music in line hold duration. Ring detector can prevent illegal dialing from pocket dialer. The SDO is designed
to drive LCD driver and voice synthesizer. In this application, the dialing numbers can be displayed on LCD
screen with EM32100 ( or EM32116 ).
FEATURES
• Tone/Pulse switchable.
•Wide operating voltage from 2.0 V to 5.5 V.
•Low operating current, 0.15 mA (Pulse) and 0.3 mA (Tone) typically.
• Adding resistor on keyboard scan pin that can select many telephone specifications, such as : Pulse rate,
M/B ratio, Flash time, lock dialing functions.
• SDO function supports LCD driver and voice synthesizer to indicate dialing numbers.
• Line hold function is designed for stopping conversation temporality.
• Melody generator provides music on hold function.
• Lock function provides conventionality key lock and password lock operations.
• Ring detector is designed to prevent illegal dialing from pocket dialer.
• 20-set one touch or (10-set one touch and 10-set two touch) repertory memory, each one can hold data up
to 16 digits.
• A 32-digit LNB (last number) redial memory.
• Keytone function provides rapidly keying recognition.
• Handfree function provides on-hook dialing and speakerphone application.
• Pause and P-T time are fixed to 3.6 seconds.
• Tone duration and inter-tone pause time are fixed to 98 ms.
• Using 3.579545 MHz crystal or ceramic resonator.
• Package forms: PDIP, skinny.
ORDERING INFORMATION
Versions list and function outline
VERSION LNB KT HOLD(music) LOCK HF SDO(LCD) PDP
EM91421A √√ √ √
EM91421B √√ √ √√
EM91421D √√ √ √√√√
Note : PDP = Pocket Dialer Prevented
EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
2
* This specification are subject to be changed without notice. 10.1.1997
EM91421
Pin Assignment
@If ROW9 and ROW10 are not connected to keyboard, The memory type is (1T*10+2T*10).
If ROW9 and ROW10 are connected to keyboard, the memory type is (1T*20) and (1T*10+2T*10).
Keyboard Arrangement
ROW10
ROW6
COL5
COL4/KT
COL3
COL2
COL1
XIN
XOUT
XMUTE
VSS
1
2
3
4
5
6
7
8
9
10
11
22
21
20
19
18
17
16
15
14
13
12
ROW9
ROW5
HDO
PO
ROW4
ROW3
ROW2
ROW1
HKS
VDD
DTMF
EM91421AK
ROW10
ROW6
COL5
COL4/KT
COL3
COL2
COL1
XIN
XOUT
XMUTE
VSS
HFI
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
ROW9
ROW5
HDO
PO
ROW4
ROW3
ROW2
ROW1
HKS
VDD
DTMF
HFO
EM91421BK
NC
ROW10
ROW6
COL5
COL4/KT
COL3
COL2
COL1
XIN
XOUT
XMUTE
VSS
HFI
DRING
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
SDO
ROW7
ROW5
HDO
PO
ROW4
ROW3
ROW2
ROW1
HKS
VDD
DTMF
HFO
RMUTE
EM91421DP
ROW1
ROW2
ROW3
ROW4
ROW5
ROW6
ROW9
ROW10
COL1
1
4
7
*/T
M1
M6
M11
M16
COL2
2
5
8
0
M2
M7
M12
M17
COL3
3
6
9
#
M3
M8
M13
M18
COL4/KT
HD
F
RD/P
M4
M9
M14
M19
COL5
PAGE
ST
M5
M10
M15
M20

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
3
* This specification are subject to be changed without notice. 10.1.1997
FUNCTIONAL BLOCK DIAGRAM
COL1
COL2
COL3
COL4/KT
COL5
XIN
XOUT
ROW1
ROW6
ROW9
ROW10
HFO HDO XMUTE
Keyboard
interface
(column)
Oscillator
Keyboard
interface
(Row)
Output circuit
Memory
(Melody)
Timing/Control circuit
Input circuit Pulse
generator
latch
&
decoder
D/A
converter
Row/Column
programming counter
DTMF
PO
HKSHFI
VDD DRING
VDD
RMUTE
SDO
~
PIN DESCRIPTIONS
Symbol Function
ROW1~ROW6 Keyboard scan pins of row group. In idle state (HKS is “High” and HFO is “Low”),
ROW9,ROW10 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.
COL1~COL3 and COL5 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.
COL4/KT 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.
XIN and XOUT 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.
XMUTE 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.
VDD and VSS Positive and negative power supply input pins. Recommended operating voltage from
2.0Vdc to 5.5Vdc.
HFI 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).
HFO 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.
DTMF 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.

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
4
* This specification are subject to be changed without notice. 10.1.1997
Symbol Function
HKS Control signal inputs pin that is corresponding hook switch status. When handset was
left from cradle, this pin must be connected to “Low” level to operate all functions.
Otherwise, this pin must be connected to “High” level to disable all function and
prevent power consumption.
PO Pulse signal outputs pin that is NMOS open-drain output structure. Normally, this pin
stays “High impedance” level. In Pulse dialing mode and keypad was entry. This pin
will output pulse trains signal that is corresponding to keyboard 0 .. 9 keys.
HDO Hold function output that is CMOS structure.Normally, this pin stays “Low” level.
When Hold function is executing, this pin will output “High” level. This pin is
designed to drive LED or peripheral circuit to indicate line is at Hold status.
SDO SDO function output that is NMOS open-drain structure. When there is a valid entry
on keyboard, this pin will output a serial data. This serial data is designed to drive LCD
driver to display dialing number on LCD screen or drive voice synthesizer to announce
dialing number to speaker.
DRING The ring signal detect input pin which is internal pull up (built-in 100 Kohms resistor).
While the Tel-ring is incoming, this pin must be connected to “Low” with delay to
indicate the ringing . Otherwise, this pin must be connected to “High” level .
RMUTE Ring mute output pin that is NMOS open-drain structure. The RMUTE pin is
designed to control microphone of handset to prevent the illegal dialing from pocket
dialer. If the DRING pin is at “High” level , then Off-Hook or turn on Handfree , this
pin will output “Low” level. In other words, the DRING pin is used to check the phone
that receives an incoming call (DRING =Low input) or make an outgoing call
(DRING= High input) . If the phone user make an outgoing call ,then RMUTE pin
activatedtopreventtheillegaldialingfrompocketdialerintheparticularapplication.The
RMUTE can be restored to “High” level when the first key entry is not the optioned
lock-number .
NC No connection.

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
5
* This specification are subject to be changed without notice. 10.1.1997
FUNCTION DESCRIPTIONS
Dialing signal selection
The EM91421 series incorporated a special keyboard scanning function that is connecting a resistor (typically
is 560 Kohms) on keyboard scan pin to select many telephone specifications. The specifications are described
as following :
a. Mode b. M/B ratio
ROW1 Mode ROW2 MBR (%)
R-Vdd 20 PPS NR 40:60
NR Tone R-Vss 33:66
R-Vss 10 PPS
c. Flash time d. Lock control method
ROW3 ROW4 Tf (ms) COL1 Control method
NR NR 600 R-Vdd key lock
NR R-Vss 100 NR none lock
R-Vss NR 80 R-Vss password lock
R-Vss R-Vss 300
e. Lock number
COL2 COL3 Lock number
NR NR none
NR R-Vss 0
R-Vss NR 9
R-Vss R-Vss 0.9
Normal dialing
Directly keying digital key on keyboard which number can be dialing output and stored in LNB memory
automatically. Operating procedure described as follow :
• To select Pulse or Tone mode.
• Off-hook or turn on HF function.
• Keying d1, d2, .. , dn. The “d” expressed digital keypad that included 1~9, *, 0, #, P, and P→T keys. The “n”
expressed unlimited.
• The numbers d1, d2, .. , dn will be dialed out in Pulse or Tone mode as selection.
LNB redial memory
Storing:
In normal dialing mode, every digital key was entry which number will be stored in LNB memory
automatically. If entry digits are more than 32 digits, the redial function of LNB memory will be disabled.
Otherwise, these numbers stored in LNB memory can be redial output.

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
6
* This specification are subject to be changed without notice. 10.1.1997
Redialing:
After normal dialing, directly keying F key (or On-Off hook once) and keying RD key on keyboard. The
numbers that are stored into LNB memory will be dialed output.
Repertory memory
The EM91421 series incorporated several sets repertory memory and each one can store number up to 16 digits.
These memories were designed to 20 sets types. As operating precedure, all of the memories can be separated
to dirtect (one-touch) and indirect (two-touch) operation. In memory storing, if stored numbers are more than
16 digits that only the previous 16 digits can be stored into specific memory. Otherwise, these numbers can be
stored entirely. After memory dialed out, the content of LNB is keeping to current data.
Storing of 20 sets memory
Direct (one-touch) operation
Off-hook (or turn on HF function), push (ST, d1, d2, .. , dn [ST], Mn.) The numbers d1, d2, .. , dn will be stored
into memory location “Mn”. The “Mn” expressed memory location M1 to M20.
Indirect (two-touch) operation
Off-hook (or turn on HF function), push (ST, d1, d2, .. , dn, [ST], Page, Mn). The numbers d1, d2, .. , dn will
be stored into memory location “Mn”. The “Mn” expressed memory location M1 to M10. The Page+M1 is
mapping to memory location M11, Page+M2 is mapping to memory location M12, ... , Page+M10 is mapping
to memory location M20.
Dialing (after memory dialed out, the content of LNB is keeping to current data)
Direct (one-touch) memory operation
• To select Pulse or Tone mode.
• Off-hook (or Turn on HF function), push Mn key. The numbers that are stored in direct memory location “Mn”
will be dialed out in Pulse or Tone mode as selection. The “n” expressed digital number from 1~20 decided
by dialers’ memory sets.
Indirect (two-touch) of 20 sets memory
• To select Pulse or Tone mode.
• Off-hook (or Turn on HF function), push Page, Mn key. The numbers that are stored in indirect memory
location “Page Mn” will be dialed out in Pulse or Tone mode as selection. The “Mn” expressed memory
location M1 to M10. The Page+M1 is mapping to memory location M11, Page+M2 is mapping to memory
location M12, ... , Page+M10 is mapping to memory location M20.

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
7
* This specification are subject to be changed without notice. 10.1.1997
Pause (P) key operation
The Pause (P) key is designed to support pause operation in dialing duration. “P” key can be stored in memory
and it will occupy one digital position.
• To select Pulse or Tone mode.
• Off-hook (or turn on HF function), push (d1, d2, .. , dn, RD/P, k1, k2, .. , kn.) These numbers will be dialed
out as following sequence:
d1, d2, .. , dn, Tp, k1, k2, .. , kn.
Pulse to Tone (*/T) key operation
The Pulse to Tone (*/T) key is designed to support toll dialing (long distance call) or PABX system operation.
The “*/T” key can be stored in memory and it will occupy one digital position.
• To select Pulse mode.
• Off-hook (or turn on HF function), push d1, d2, .. , dn, */T, k1, k2, .. , kn. These numbers will be dialed out
as following sequence:
d1, d2, .. , dn, Tpt, k1, k2, .. , kn.
(pulse mode) (tone mode)
Flash (F) key operation
The Flash (F) key is designed to break telephone line temporarily. After F key is depressed, this dialer will send
a flash signal to break line 600 ms, 300 ms, 100 ms or 80 ms as ROW3 and ROW4 selection.
Handfree (HF) function
The handfree function is designed to support on-hook dialing and loudspeaker application which can be turn “on”
or “off” with falling edge signal from HFI pin. During handfree function is executed, the HFO pin is switched
to “high”. Otherwise the HFO pin stays “low” level. One of the following operations can turn off Handfree
function (HFO pin return to “Low”).
• On-off hook once.
• Trigger HFI pin with falling edge signal.
• Turn on Hold (HD) function. (HDO pin switched to “High”)
Hold (HD) function
The Hold function is designed to stop conversation temporarily. In off-hook state (or HF function is turned on),
to press HD key on the keyboard, the Hold function can be turned “on” (HDO pin switched to “High”). One of
the following operations can turn off Hold function (HDO pin switched to “Low”).
• On-off hook once.
•To press HD key over 280 ms.
• Turn on Handfree (HF) function. (HFO pin switched to “High”)
Special Note:

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
8
* This specification are subject to be changed without notice. 10.1.1997
A 300 ms delay time (Tdly) at the first Off-Hook or turn on Handfree that is a special designed to avoid a rapid
key entry (dummy number ) in this time duration ,and a long distance call number follows. For example,
Off-Hook , “3” ,............ , “0” ,1,2,3......
Dummy key Lock number key
The dummy number “3” is not detected by the centered office or PABX ,but the following numbers “0” ,1,2,3...
long distance call can be dialed out normally since the leading number “3” is not the Lock-number defined in
EM91421 series. To prevent the unavoidable long distance call, then EM91421 series inhibits the key entry during
Tdly.

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
9
* This specification are subject to be changed without notice. 10.1.1997
Operating flow chart
<Note> : HF = Handfree
HD = Hold
Truth table
Operating state Input/Output pin level
HKS PO XMUTE HFO HDO
(0) On-hook, idle state H F F L L
(1) Off-hook line L F F L L
(2) Off-hook, HF line L F F H L
(3) On-hook, HF line H F F H L
(4) Off-hook, HD line L F L L H
(5) On-hook, HD line H F L L H
Note : F=floating (high impedance); H=logic “High”; L=logic “Low” level.
Music on Hold
EM91421 series built-in a melody generator to generate dual-tone music on DTMF output pin. The music is
designed for telephone line at line holding.
01 bit 0 bit1 bit2 bit3 bit4 bit5
ready start bits data bits 01
stop bits
SDO (Serial Data Output) function
The SDO is serial data output which format is same as UART protocol. SDO function is designed to drive LCD
driver and voice synthesizer. So the dialing numbers can be display on LCD screen with EM32100 (or EM32116
). The SDO signal consists of two start bits, six data bits and two stop bits. Each bit time is about 3.9 ms (256 Hz)
and output sequences are following by start bits, data bits (LSB to MSB) and stop bits.
1
On-hook State
2
Off-hook State
4
On-hook
Hand-free State
HKS=Lo
HKS=Lo
HKS=Hi
HF
HF
HD HF
HD 6
On-hook
Hold-line State
3
Off-hook
Hand-free State
HF
HF
HF
HD
HKS=Hi
HKS=Lo
5
Off-hook
Hold-line State
HD
HD
HKS=Hi

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
10
* This specification are subject to be changed without notice. 10.1.1997
∗Keypad,SDO format and LCD display reference table:
Keypad bit5 bit4 bit3 bit2 bit1 bit0 Display
1000001 1
2000010 2
3000011 3
4000100 4
5000101 5
6000110 6
7000111 7
8001000 8
9001001 9
0001010 0
“*”/T 0 0 1 0 1 1 
#001100 
P001101 P
*/”T” 0 0 1 1 1 0
ST 1 0 0 0 0 0 STORE
HOLD 1 0 1 0 0 0 HOLD
HF 1 0 1 0 1 0 Speaker
PAGE 1 0 1 1 0 0 PAGE
F 1 0 1 1 1 1 clear all display
(Lock state) 1 0 0 0 0 1 Lock
M1~M20 1 1 1 1 0 0 MEMORY
RD 1 1 1 1 0 1 RD
SDO Keypad Encoded table:
♦Digital key (b5,b4=0,0)
keypad 1 2 3 4 5 6 7 8 9 0 “*”/T # P */”T”
output
b3,b2,b1,b0 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110
Display 1 2 3 4 5 6 7 8 9 0  P
♦ Function key (b5,b4=1,0)
keypad ST Hold HF Page F (Lock state)
output
b3,b2,b1,b0 0000 1000 1010 1100 1111 0001
Display STORE HOLD Speaker PAGE clear all display Lock
♦Function key (b5,b4=1,1)
keypad M1~M20 RD
output
b3,b2,b1,b0 1100 1101
Display MEMORY RD
<Note> : The display of LCD panel “ST”,”Hold”,”HF”,”Page”,M1~M20”,”RD” is corresponding to EM32116
with flag types.

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
11
* This specification are subject to be changed without notice. 10.1.1997
LOCK function
The EM91421 series provides the LOCK function to inhibit toll dialing operation. Connecting a resistor on COL1
pin to VSS can select different LOCK control method that is conventional key lock or password lock. Also the
lock number that can be selected by connecting the resistors on COL2 or COL3 pin. After power on reset, the
password is fixed to 000 automatically. The lock function is disabled when the password is equal to 000 .
How to setup password
• Set LOCK function to password control mode. (Connects a resistor on COL1 pin to VSS)
• Off hook (or turn on HF function)
• Push : # , # , ops1 , ops2 , ops3 , nps1 , nps2 , nps3 , # . If the ops1~ops3 are the same with current password,
then nps1~np3 will be stored in the dialer to replace current password. Otherwise, the current password can
not be updated. All the numbers pressed in the password setup procedure can not be dialed out when current
password is not equal to 000. If the current password are equal to 000, then only the first number “#” will be
dialed out.
Normal dialing :
Set lock function to none lock mode (without resistor connected to COL1 pin) or set password equal to 000.
In this case, the dialer is operated in normal mode and all functions work at unlimitation.
Dialing via LOCK function
Conventional key lock mode. (Connects a resistor on COL1 pin to VDD)
• Off hook (or turn on HF function)
• Keying : d1 , d2 , .. , dn . If the first number (d1) is the same with the lock number that optioned in table,
then all entry numbers can not be dialed out and keyboard will be inhibited until on to off hook once again.
If the first number is not equal to lock number, all the entry numbers will be dialed out.
Password control mode. (Connects a resistor on COL1 pin to VSS)
• Off hook (or turn on HF function)
• Keying : ([ # , ps1 , ps2 , ps3 ] + telephone number.) The numbers in the [ ] symbol could be omitted. The
number “#” will be inhibited when the current password is not equal to 000,and ps1 , ps2 , ps3 work at the
checking state, not to be dialed out. Other descriptions are as on following :
◊Incorrect password entry. The telephone numbers can not be dialed out.
◊Password is omitted . If the first digit of telephone numbers is the same with the lock number, all of the
telephone numbers can not be dialed out and keyboard will be inhibited until On to Off hook once again.
If the first digit is not equal to the lock number then the telephone numbers will be dialed out entirely.
◊Correct password entry. The telephone numbers can be dial out no matter what lock number is.
Ring detector
The Ring detector is designed to prevent illegal dialing from pocket dialer. Following the procedures ( i,ii,iii ),
this dialer will detect DRING pin to control RMUTE output level. If DRING is detected a “Low” level, the
RMUTE stays “High impedance”. If DRING is detected a “High” level, the RMUTE will output “Low” until

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
12
* This specification are subject to be changed without notice. 10.1.1997
keyboard entry. In actual application of the RMUTE pin is recommended connection to microphone of the
phone handset to prevent that the dialing signal (DTMF) is coupling by the Microphone of the phone handset.
(such as pocket dialer)
i. In idle state, HKS is from “High” to “Low” (pick up handset action).
ii. In idle state, turn on handfree function.
iii. The flash operation ( F key ).
ABSOLUTE MAXIMUM RATINGS(Ambient temperature is 25 °C, all voltages referenced to VSS)
Items Sym. Rating Unit
Power supply voltage VDD 6.0 Vdc V
Input voltage range VIN VSS-0.3V ~ VDD+0.3V V
Operating temperature TOPR 0 ~ +50 °C
Storage temperature TSTO -55 ~ 125 °C
Power consumption PD500 mW
ELECTRICAL CHARACTERISTICS
(Ambient temperature is 25 °C, VDD=2.5V unless otherwise noted, all voltages referenced to VSS, Fosc=3.579545 MHz)
Parameter Sym. Min. Typ. Max. Unit Condition
Operating voltage Pulse 2.0 - 5.5 V unload
Tone 2.0 - 5.5
Operating current(HKS=0) Pulse Idd - 0.15 0.3 unload
Tone - 0.3 0.5 mA
Pulse - 0.15 0.3 with pull up/down
Tone - 0.3 0.5 resistor * 8
Memory retention current Imrt - 0.001 0.1 uA HKS=1,Vdd=1V
Standby current HKS=1 Istby - 0.001 0.1 unload
HKS=0 - 1 10 uA
HKS=1 -0.001 0.1 with pull up/down
HKS=0 - 10 30 resistor * 8
HKS, HFI & DRING ViH 0.8Vdd - Vdd V
pins: input voltage ViL Vss - 0.2Vdd
HFO & HDO pins source current IoH 0.2 - - mA Vo = 2.0 V
PO, HFO, XMUTE, RMUTE IoL -0.2 - - mA Vo = 0.5 V
& SDO pins: sink current
PO, XMUTE, RMUTE and SDO IoH - - ±0.001 uA Vo = Vdd
pins: leakage current
HFI pin input resistance Rhfi - 200 - KΩVhfi = Vss
DRING pin input resistance Rdring - 100 - KΩVdeing=Vss
Keyboard scanning pins IoH 2 10 50 uA Vksn=Vss
output current (except COL4/KT) IoL 200 400 800 V ksn=Vdd
COL4/KTsource current IoH 0.2 - - mA Vo=2.0V
sink current IoL 0.2 - - Vo=0.5V

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
13
* This specification are subject to be changed without notice. 10.1.1997
Parameter Sym. Min. Typ. Max. Unit Condition
ELECTRICAL CHARACTERISTIC
(Ambient temperature is 25°C, VDD=2.5V unless otherwise noted, all voltages referenced to Vss,Fosc=3.579545 MHz)
○○○○○○○○○○○○○○○○○○○
○○○○○○○○○○○○○○○○○○○
○○○○○○○○○○○○○○○○○○○
○○○○○○○○○○○○○○○○○○○
○○○○○○○○○○○○○○○○○○○
○○○○○○○○○○○○○○○○○○○
Keyboard debounce time Tdb - 20 - ms
Key tone signal:
frequency Fkt - 600 - Hz
duration Tkt - 30 - ms
Pause time Tp - 3.6 - sec.
Pulse to Tone waiting time Tpt - 3.6 - sec.
Flash time Tf - 600 - Row3B, Row4B=NR, NR
- 100 - ms Row3B, Row4B=NR, R-Vss
- 80 - Row3B,Row4B=R-Vss, NR
- 300 - Row3B,Row4B=R-Vss,R-Vss
Pulse rate PSR - 20 - pps Row1 = R-Vdd
- 10 - Row1 = R-Vss
Make/Break ratio MBR - 40:60 - % Row2 = NR
- 33:66 - Row2 = R-Vss
Inter-digit pause time Tidp - 800 - ms PSR = 10 pps
- 500 - PSR = 20 pps
DTMF pin: sink current IoL -0.2 - - mA Vdtmf = 0.5 V
DTMF signal DC level Vdc 0.5 - 0.75 Vdd Vdd = 2.0V ~ 5.5V
DTMF signal: ac level Vdtmf 142 160 180 mVrms Row group
pre-emphase Twist 1 2 3 dB Column - Row
distortion THD - -30 -23 dB RL = 5 KΩ
load resistance ZL 5 - - KΩTHD < − 23dB
Minimum tone duration Tp 96 98 100
Minimum inter-tone pause Titp 96 98 100 ms Memory dialing
Melody output signal:
main tone ac level (-23.3) (dBm)
Vmtac 48 53 58 mVms Vdd =2.0V ~ 5.5V
Sub-tone (-25.3) (dBm)
Vstac 37 42 47 mVms Vdd =2.0V ~ 5.5V
HD key release hold function Thdrdb - 280 - ms
debounce time
SDO every bit time Tbit 3.8 3.9 4.1 ms
Off-Hook delay time Tdly - 300 - ms

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
14
* This specification are subject to be changed without notice. 10.1.1997
DTMF output frequency (fosc = 3.579545 MHz)
Keyboard scan pin CCITT standard (Hz) Actual output (Hz) Deviation (%)
ROW1 (f1) 697 699.1 0.30
ROW2 (f2) 770 766.2 0.49
ROW3 (f3) 852 847.4 -0.53
ROW4 (f4) 941 947.9 0.73
COL1 (f5) 1209 1215.8 0.56
COL2 (f6) 1336 1331.6 -0.32
COL3 (f7) 1477 1471.8 -0.35

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
15
* This specification are subject to be changed without notice. 10.1.1997
TIMING DIAGRAM
Figure 1. Pulse mode operating timing
Figure 2. DTMF mode operating timing
HKS
KEY IN
KT
XMUTE
HDO
SDO
PO
DTMF
OSC.
Tdb
Tkt
23
Tm
Tidp T
bT
mT
bT mTidp
Tdly
Hi-impedance
HKS
KEY IN
KT
XMUTE
HDO
SDO
PO
DTMF
OSC.
Tdb
23
Td Titp Titp
Hi-impedance

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
16
* This specification are subject to be changed without notice. 10.1.1997
Figure 3. Pulse mode LNB redial timing
HKS
KEY IN
KT
XMUTE
HDO
SDO
PO
DTMF
OSC.
Tdb
Tkt
RD/P
Tm
Tidp T
bT mT
bT m
Tidp
Tdly
LNB=2,3
Hi-impedance
Figure 4. DTMF mode LNB redial timing
HKS
KEY IN
KT
XMUTE
HDO
SDO
PO
DTMF
OSC.
Tdb
Tkt
RD/P
Td
Tdly
Hi-impedance
LNB=2,3
Td
Titp Titp

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
17
* This specification are subject to be changed without notice. 10.1.1997
Figure 6. Pulse to Tone (P→T) operating timing
Figure 5. Pause key operating timing
Tidp Tidp
Tp
2RD/P 3
HKS
KEY IN
KT
XMUTE
HDO
SDO
PO
DTMF
OSC.
Hi-impedance
Tpt
PO
HKS
KEY IN
KT
XMUTE
HDO
SDO
DTMF
OSC.
2 */T 34
Hi-impedance
HKS
KEY IN
KT
XMUTE
HDO
SDO
PO
DTMF
OSC.
Tdb
Tf Tfp=300ms
Hi-impedance
F
Figure 7. Flash key operating timing

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
18
* This specification are subject to be changed without notice. 10.1.1997
Figure 8. SDO operating timing
<Note>L=LSB,M=MSB, sT=START bit time, spT=STOP bit time
HF HD HF HD HF HD HD HD HD @
280
ms Thdrdb
HKS
KEY IN
HFO
HDO
XMUTE
SDO
PO
MELODY
Hi-impedance
Figure 10. Off-Hook delay time
Tdly
"0" digit dialing time
0
5
HF
HFI
or
HKS
KEY
KT
OSC.
Hi-impedance
@ : It can be triggled by extension telephone set for hold function release
Figure 9. HF and HD operating timing
HKS
KEY IN
KT
SDO
Tdb
2
sT
sT b0
b1 b2 b3 b4 b5 spT spT
0101000001
Tbit
LM
Hi-impedance

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
19
* This specification are subject to be changed without notice. 10.1.1997
RING
DRING
HKS
RMUTE
Toff
Ton
Figure 11. Timing of receiving an incoming call
Figure 12. Timing of making an outgoing call
RING
DRING
HKS
RMUTE
* The external ring detection circuit must send a low signal at the total ring cycle (Ton and Toff)

EM91421 SERIES
TONE/PULSE SWITCHABLE DIALER WITH LCD INTERFACE
AND DUAL-TONE MELODY GENERATOR
20
* This specification are subject to be changed without notice. 10.1.1997
APPLICATION CIRCUIT
EM91421 series Application circuit
HANDSET HANDFREE
5 4
6
SW1B
BRIDGE
TIP
470
ONHOOK
OFFHOOK
2 1
3
SW1A
1
2
3Q6
A92
R47
220K
R54 10M
R48
100K
1 2
D6
1N4148 1 2
D7
1N4148
R49
2K7
R52
220K
C16 .001U
R36 470K
R33
1K5
1 2
3 Q18
1815
HOOK
HFO
R55 470K
EM32100
JP9 1
2
3 Q14
C945
1 2
D16
1N4148
1 2
D17
1N4148
R56 47K
CE
ROW1
1 2
D18
1N4148
HDO
EM32100
JP10
R65 220K
C17
.01U
1 2
3 Q19
1815
R67
50
C23
47U
C24
.1u
C31
220uF D13
5V1
1 2
3 Q4
C945
R37
100K
C25 .1U
R35
2K2
2
1
3Q7
A42
1
2
D14 1N4148
R69 47K
RING
BRIDGE
.1U
22U/50V
R68
100K
VDD
27V 12 D5
1N4148
R43 47K
12 D19
1N4148
R57 47K
R44
22K
R45 47K
C21
.1uF
C22 1uF
1 2
3 Q9
C945
R46 10K
HDO 1
2
3 Q10
C945 AUDIO
POWER
AMPLIFER
COL4/KT
CE JUMPER
560K
560K
560K
560K
DRING
4K7 1.2M
1U
1
2
4
3
PC817
1 4 7
*/T M1 M5
M11 M16
2 5 8 0
M2 M7
M12 M17
3 6 9 #
M3 M8
M13 M18
HD
F
RD/P
M4 M9
M14 M19
PAGE
ST
M5
M10 M15 M20
ROW5
ROW6 ROW9
ROW10
JUMPER
JUMPER
VDD
560k
EM91421DK
SDO
LCD DRIVER
VCC
1.5V
2 TO 4 LINE
SPEECH NETWORK
DRING
3.58MHz
R? 560k R?
560k R?
560k BUZZER
10p 10p
HF
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
SDO
ROW9
ROW5
HDO
PO
ROW4
ROW3
ROW2
ROW1
HKS
VDD
DTMF
HFO
RMUTE
NC
ROW10
ROW6
COL5
COL4/KT
COL3
COL2
COL1
XIN
XOUT
XMUTE
VSS
HFI
DRING