ACS411CS datasheet(10/43 Pages) SEMTECH

10 / 43 page

ACS411CS PRE-RELEASE Issue 6.0 July 1999.

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.

Diagnostic Modes and Configuration

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.

Transmit and Receive Clock

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.

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.

Remote Loopback

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.

Maintenance channel

The ACS4110 offers up to 2 synchronous maintenance

channel consisting of the following signals:

Transmit Side

TMD1

transmit NRZ data/framing

TMD2

transmit NRZ data/framing

TmCLK

transmit clock (internal or external)

Receive Side

RMD1

receive NRZ data/framing

RMD2

receive NRZ data/framing

RmCLK

receive clock

Maintenance Data Rate Selection

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.

MSEL(3:1)

Data Rate (kbps)

101

100

011

010

001

128

000

256

Table 7: Maintenance Channel Data Rate Selection

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