AMIS-49587_15 Datasheet, PDF (16/56 Pages) ON Semiconductor – Power Line Carrier Modem

AMIS−49587
5 INTRODUCTION
5.1 GENERAL DESCRIPTION
The AMIS−49587 is a single chip half duplex S−FSK
modem dedicated to power line carrier (PLC) data
transmission on low− or medium−voltage power lines. The
device offers complete handling of the protocol layers from
the physical up to the MAC. AMIS−49587 complies with the
CENELEC EN 50065−1 and the IEC 61334−5−1 standards.
It operates from a single 3.3 V power supply and is
interfaced to the power line by an external power driver and
transformer. An internal PLL is locked to the mains
frequency and is used to synchronize the data transmission
at data rates of 300, 600, 1200 and 2400 baud for a 50Hz
mains frequency, or 360, 720, 1440 and 2880 baud for a
60 Hz mains frequency. In both cases this corresponds to
3,6,12 or 24 data bits per half cycle of the mains period.
S−FSK is a modulation and demodulation technique that
combines some of the advantages of a classical spread
spectrum system (e.g. immunity against narrow band
interferers) with the advantages of the classical FSK system
(low complexity). The transmitter assigns the space
frequency fS to “data 0” and the mark frequency fM to “data
1”. The difference between S−FSK and the classical FSK
lies in the fact that fS and fM are now placed far from each
other, making their transmission quality independent from
each other (the strengths of the small interferences and the
signal attenuation are both independent at the two
frequencies). The frequency pairs supported by the
AMIS−49587 are in the range of 9−95 kHz with a typical
separation of 10 kHz.
The conditioning and conversion of the signal is
performed at the analog front−end of the circuit. The further
processing of the signal and the handling of the protocol is
digital. At the back−end side, the interface to the application
is done through a serial interface. The digital processing of
the signal is partitioned between hardwired blocks and a
microprocessor block. The microprocessor is controlled by
firmware. Where timing is most critical, the functions are
implemented with dedicated hardware. For the functions
where the timing is less critical, typically the higher level
functions, the circuit makes use of the ARM 7TDMI
microprocessor core.
The processor runs DSP algorithms and, at the same time,
handles the communication protocol. The communication
protocol, in this application, contains the MAC = Medium
Access Control Layer. The program running on the
microprocessor is stored into ROM. The working data
necessary for the processing is stored in an internal RAM. At
the back−end side the link to the application hardware is
provided by a Serial Communication Interface (SCI). The
SCI is an easy to use serial interface, which allows
communication between an external processor used for the
application software and the AMIS−49587 modem. The SCI
works on two wires: TXD and RXD. Baud rate is
programmed by setting 2 bits (BR0, BR1).
Because the low protocol layers are handled in the circuit,
the AMIS−49587 provides an innovative architectural split.
Thanks to this, the user has the benefit of a higher level
interface of the link to the PLC medium. Compared to an
interface at the physical level, the AMIS−49587 allows
faster development of applications. The user just needs to
send the raw data to the AMIS−49587 and no longer has to
take care of the protocol detail of the transmission over the
specific medium. This last part represents usually 50 percent
of the software development costs.
CLIENT
Application
AMIS−49587 in
MASTER mode
SERVER
Application
AMIS−49587 in
SLAVE mode
SERVER
Application
AMIS−49587 in
SLAVE mode
SPY
Application
AMIS−49587 in
MONITOR mode
TEST
Application
AMIS−49587 in
TEST mode
Major User Type
Figure 8. Application Examples
Minor User Type
AMIS−49587 intended to connect equipment using
Distribution Line Carrier (DLC) communication. It serves
two major and two minor types of applications:
• Major types:
♦ Master or Client:
A Master is a client to the data served by one or
many slaves on the power line. It collects data from
and controls the slave devices. A typical application
is a concentrator system.
♦ Slave or Server:
A Slave is a server of the data to the Master. A
typical application is an electricity meter equipped
with a PLC modem.
• Minor type:
♦ Spy or Monitor:
Spy or Monitor mode is used to only listen to the
data that comes across the power line. Only the
physical layer frame correctness is checked. When
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