ACS101A データシートの表示（PDF） - Semtech Corporation
部品番号
コンポーネント説明
一致するリスト
ACS101A Datasheet PDF : 12 Pages
| |||
Acapella Optical Modem IC
ACS101A
Synchronous or Asynchronous Single Fiber Modem
Inter-IC Encoding Technique
The 3B4B encoding method is used for communication between
ACS101A, thus ensuring that there is no DC component in the
signal. The encoding and decoding is transparent to the user.
For data-rates of 9.6, 19.2, 33.4, 48 and 64kbps the data-rate
selection pins DR1-DR3 are common to standard and double
modes of operation, with DR4 selecting the distance mode.
Modem Control Signals
Transmitter and Receiver Functions
RSS.
The TxD input data of the transmitting modem is compressed,
filtered, and 3B4B encoded. In the receiving modem, 3B4B
encoding ensures easy extraction of the bit-clock. The received
data is filtered, decoded, then stored in an output memory. The
memory provides time expansion, de-jittering and frequency
compensation. Finally, the data is filtered again to improve BER
then directed to the RxD output pin.
RTS, CTS, DTR and DSR signals may be used in either of two
modes, depending on the RSS setting:
RSS = Low; data transmission mode
RSS = High; modem handshake mode
RSS Low - Data Transmission Mode.
Transmit Current
In data transmission mode the inputs RTS and DTR are sampled
continuously at (crystal freq.) / 1536, 6.0kHz with a crystal of
The transmit current to the LED can be defined by the Transmit 9.216MHz. The outputs appear at CTS and DSR respectively.
2
Current pin (TRC). The current is set to the maximum value
RSS High - Modem Handshake Mode.
(~100mA) when TRC is unconnected. The current is set to the
minimum value (~10mA) when TRC is connected directly to In modem handshake mode the control signals are used as
ground. To obtain current values between minimum and maximum conventional handshake signals between the DTE (terminal) and
TRC is connected to ground through a resistor. The resistor value the DCE (modem):
R is given by:
LED current drive (mA) =
100 * (110+R)
(1100+R)
DSR (Data Set Ready) DCE à DTE.
The DCE is powered up and asserts a Low (active level) on DSR.
The DTE is informed that it is connected to a “live” DCE.
Data-rate Selection DR1 to DR4
Modes for Asynchronous Data :
DR4 DR3 DR2 DR1 XTAL freq Data-rate
(MHz)
(kbps)
Distance
DTR (Data Terminal Ready) DTE à DCE.
The DTE is powered-up and asserts a Low (active level) on DTR.
The DCE is informed that it is connected to a “live” DTE. If DTR is
set High, the DCE responds by asserting DCDB High.
01 1 0
11 1 0
11 1 0
9.216
9.216
18.432
DC - 19.2
DC - 38.4
DC - 76.8
Double
Standard
Short
Modes for Synchronous Data :
DR4 DR3 DR2 DR1 XTAL freq Data-rate
(MHz)
(kbps)
Distance
00 0 1
00 1 0
00 1 1
01 0 0
01 1 1
10 00
10 0 1
10 1 0
10 1 1
11 0 0
11 0 1
11 1 1
01 0 1
00 0 0
00 0 0
9.216
9.216
9.216
9.216
9.216
9.216
9.216
9.216
9.216
9.216
9.216
9.216
9.216
9.216
18.432
9.6
19.2
38.4
48.0
64.0
2.4
9.6
19.2
38.4
48.0
56.0
64.0
192.0
256.0
512.0
Double
Double
Double
Double
Double
Standard
Standard
Standard
Standard
Standard
Standard
Standard
Standard
Standard
Short
Standard' mode of operation is up to 2.5km, 'double' mode is up to
5km and 'short' is up to 1.25km. Other non-standard data-rates
may be generated by using different crystal frequencies as long as
the 5 - 19MHz crystal range is observed.
RTS (Request to Send) DTE à DCE.
The DTE recognises that synchronisation has been achieved
(DCDB active) and asserts a Low (active level) on RTS. This
constitutes a request by the DTE to send data to the far-end
modem.
CTS (Clear to Send) DCE à DTE.
The DCE recognises the active RTS signal and responds by
asserting a Low (active level) on CTS. If RTS is set High the DCE
responds by bringing CTS High.
DCDB (Data Carrier Detect) DCE à DTE.
When synchronisation is achieved between DCEs the DCDB
signal is set Low (active level). If synchronisation is lost the DCE
sets DCDB and CTS High.
Crystal Clock
A crystal may be connected between the pins XLI and XLO.
Alternatively, XLI may be driven directly by an external clock. The
operational frequency range is 5MHz to 19MHz, though
communicating devices must be driven at the same nominal
frequency with a tolerance of 100ppm. In synchronous mode the
frequency should be 9.216MHz, resulting in the standard range of
synchronous communication frequencies selected by DR1-DR4.
ACS101A Issue 1.2 October 1999.
2
Share Link: 