ACS411CS Semtech Corporation, ACS411CS Datasheet - Page 10

• Manufacturer Part Number: ACS411CS
• Description: Acapella Optical Modem ic
• Manufacturer: Semtech Corporation

ACS411CS PRE-RELEASE Issue 6.0 July 1999.
loopback test can be initiated via the microprocessor
interface (in all microprocessor modes), giving
independent control for each channel. All channels
can be simultaneously initiated into local loopback
when the microprocessor mode is disabled via the
CM(3:1) pins.
In remote loopback mode, both modems are
exercised completely, as well as the Lasers/LEDs
and the fiber optic link. The remote loopback test is
normally used to check the integrity of the entire link
from the near-end (initiating modem).
Whilst a device is responding to a request for remote
loopback from the far-end, requests from the near-
end to initiate remote loopback will be ignored.
The remote back request can be initiated by either
the near end modem (the near-end modem sends a
request to the far-end modem to loopback its received
data) or by the far end modem itself. In both cases
the far end modem loops back the received data to
the near end.
The remote loopback test can be initiated via the
microprocessor interface (in all microprocessor
modes), giving independent control for each channel.
All channels can be simultaneously initiated into
remote loopback when the microprocessor mode is
disabled via the CM(3:1) pins.
The ACS4110 offers up to 2 synchronous maintenance
channel consisting of the following signals:
Transmit Side
TMD1
TMD2
TmCLK
Receive Side
RMD1
RMD2
RmCLK
The data rate can be selected via the maintenance
data rate selection bits MSEL(3:1), either directly via
pins or via the microprocessor interface.
TMD1/RMD1 and TMD2/RMD2 support up to 256kbps
synchronous data synchronised to TmCLK/RmCLK.
They can be used as two independent channels giving
a total available bandwidth to 512kbps.
Alternatively, TMD1 or TMD2, together with a specific
data rate selection, can be used to divide the bandwidth
of the remaining maintenance channel into sub-
channels with a certain data rate, defined in Table 7.
Remote Loopback
Maintenance channel
Maintenance Data Rate Selection
transmit clock (internal or external)
transmit NRZ data/framing
transmit NRZ data/framing
receive NRZ data/framing
receive NRZ data/framing
receive clock
10
For example: 4 x 16kbps maintenance channels.
select MSEL(3:1) = 010, total available bandwidth on
TMD1 is 64kbps and frame every 4th bit. The "framing"
channel TMD2 is bit locked to the data channel TMD1.
The diagnostic and configuration modes available for
the main channels are also available for the
maintenance channels. CM(3:1) also controls the
maintenance channels, while all modes including
remote loopback and local loopback are also selectable
individually via the microprocessor interface.
The ACS4110 gives the choice between internally or
externally generated TmCLK under the control of the
CKM pin. When the CKM pin is held Low, TmCLK
is configured as an output producing a clock at the
data rate determined by MSEL(3:1). When the CKM
pin is held High, TmCLK is configured as an input,
and will accept an externally produced transmission
clock at the data rate determined by MSEL(3:1).
Input data appearing on the TMD1/2 inputs is latched
into the device on either the rising or falling edge of
the TmCLK clock depending on the setting of TRSEL.
This data appears at the RMD1/2 outputs of the far-
end modem on the rising or falling edge of the
RmCLK clock depending on the setting of RESEL
( see Figure 21. Timing diagrams ). To ensure that
the average receive frequency is the same as the
transmitted frequency, RmCLK is generated from a
Digital Phase-Lock Loop (DPLL) system.
Whilst the TMD1/RMD1 and TMD2/RMD2
maintenance channels have a fixed phase
relationship with each other, they do not have a fixed
phase relationship with the main TPOS/TNEG data
transmission channels.
Diagnostic Modes and Configuration
Transmit and Receive Clock
Table 7: Maintenance Channel Data Rate Selection
MSEL(3:1)
101
100
011
010
001
000
Data Rate (kbps)
128
256
16
32
64
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