Data Sheet
AS2574B
20 NUMBER ONE TOUCH DIALLER WITH
SERIAL BUS FOR DISPLAY DRIVER
Austria Mikro Systeme International
General Description
KeyFeatures
The AS2574B is an integrated CMOS device for feature
telephones. It is a very versatile LD/MF dialler with serial
interfacetoadisplaydriver. Thedeviceisdesignedtobe
used in a wide variety of applications together with the
companion display driver, AS2590.
❑ Low operating voltage (2.5V to 5.5V)
❑ Low current consumption (typ. 200 µA in LD mode)
❑ Oscillator using ceramic resonator (681 kHz)
❑ MF level independent of supply voltage
❑ Direct ´wake-up´ from keyboard
❑ Automatic Call Progress by direct memory key
❑ Data protection with 8 digit FIFO
The on chip RAM can contain up to 20 memories (each
with maximum 18 digits), a 36 digit Last Number Redial
(LNR) and an 18 digit notepad. Access to the 20 memo-
ries is either with direct keys, abbreviated dial code or a
combination of both. The AS2574B provides a unique
feature, Automatic Call Progress (ACP), on all memory
keys, i.e. the circuit automatically seizes the line and
waits for the dial tone and dials the number just by
pressing any of the memory keys (including LNR).
❑ Sliding cursor protocol with comparison
❑ Diode options for different PTT requirements
❑ Automatic pause generation after access code
❑ Temporary MF select via keyboard
❑ 36 digit LNR (Last Number Redial)
❑ 20 memories addressable with direct keys and the
2nd key or indirect with a MEM key
❑ Notepad
❑ Serial interface to display driver AS2590
❑ Consistent, simple and useable procedures
❑ Input for dial tone recognizer
The circuit features 2 different access code procedures
to allow easy use under a PABX. A dial tone input
enables the use of a dial tone recognizer.
Application
Package
High feature telephone sets.
Available in 28 pin DIP and PLCC.
La
Directwake-upisanAMSpatented
solutionprovidinglineseizingwith
Lb
a telephone, that is entirely
powered from the telephone line,
E
by pressing a key in a key matrix
Flash
DP
ER
connected to a dialler/controller
that is constantly connected to the
Ground
Loop
R1
R2
R3
SPEECH
1
4
7
2
5
3
6
9
#
ENTER M1
M5
VDD
HS
M2
R
M6
M7
M8
LOUDHEARING
HANDSFREE
TONE RINGER
line by means of a line voltage
limiter and yet maintaining a high
dcisolationresistanceinidlestate
(on-hook).
8
2ND M3
MUTE M4
MASK
TONE
0
R4
R5
*
681kHz
LNR
M9 MEM M10
LS
OSC1
OSC2
TB
C6
C5
C4
C3
C2
C1
MODE
ACP
M/B
MS
AS2574BCD
The wake-up feature allows the
user to go off-hook by pressing a
MT
MR
LS
Vss
SCL
SDA
direct memory key or
a
VDD
SDA
MS
loudspeaker key, so-called on-
hook dialling or call progress
monitoring, and thereby seize the
line.
SCL
V23
32.768kHz
X1
X2
V13
BIAS
VLCD
Vss
DISPLAY
Jan. 1995
1
Rev. 1