Data Sheet
AS2574B
Rev. 1 1 Jan. 1995
Package
Available in 28 pin DIP and PLCC.
20 NUMBER ONE TOUCH DIALLER WITH
SERIAL BUS FOR DISPLAY DRIVER
Austria Mikro Systeme International
Key Features
a75 Low operating voltage (2.5V to 5.5V)
a75 Low current consumption (typ. 200 µA in LD mode)
a75 Oscillator using ceramic resonator (681 kHz)
a75 MF level independent of supply voltage
a75 Direct ´wake-up´ from keyboard
a75 Automatic Call Progress by direct memory key
a75 Data protection with 8 digit FIFO
a75 Sliding cursor protocol with comparison
a75 Diode options for different PTT requirements
a75 Automatic pause generation after access code
a75 Temporary MF select via keyboard
a75 36 digit LNR (Last Number Redial)
a75 20 memories addressable with direct keys and the
2nd key or indirect with a MEM key
a75 Notepad
a75 Serial interface to display driver AS2590
a75 Consistent, simple and useable procedures
a75 Input for dial tone recognizer
General Description
The AS2574B is an integrated CMOS device for feature
telephones. It is a very versatile LD/MF dialler with serial
interface to a display driver. The device is designed to be
used in a wide variety of applications together with the
companion display driver, AS2590.
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).
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.
SDA
SCL
R5
C6
C5
C4
C3
C2
C1
VDD
HS
TONE
DP
R1
R2
R3
R4
ER
Vss
TB
AS2574B
DIALLER/CONTROLLER
La
Lb
E
LS
CD
MR
MT
M4 M8
M7
M6
M5
M2
M1
M3
MASK
OSC1
OSC2
681kHz
MUTE
R
ENTER
2ND
#
6
3
9
0
5
2
8
*
4
1
7
M10MEMM9LNRLS
SDA
SCL
VDD
X1
X2
V23
V13
VLCD
BIAS
MS
Vss
AS2590
32.768kHz
DISPLAY
MODE
ACP
M/B
MS
Flash
Ground
Loop
SPEECH
LOUDHEARING
HANDSFREE
TONE RINGER
Application
High feature telephone sets.
Direct wake-up is an AMS patented
solution providing line seizing with
a telephone, that is entirely
powered from the telephone line,
by pressing a key in a key matrix
connected to a dialler/controller
that is constantly connected to the
line by means of a line voltage
limiter and yet maintaining a high
dc isolation resistance in idle state
(on-hook).
The wake-up feature allows the
user to go off-hook by pressing a
direct memory key or a
loudspeaker key, so-called on-
hook dialling or call progress
monitoring, and thereby seize the
line.
