ACS406CS Semtech Corporation, ACS406CS Datasheet - Page 10

• Manufacturer Part Number: ACS406CS
• Description: Two-chip Fiber Optic Modem Ics / ACS4060 100-pin Tqfp, ACS9010 44-pin TQFP
• Manufacturer: Semtech Corporation

When Frame = 0 then maintenance mode is selected.
One maintenance channel TmD1/RmD1 is available
when TX1, TX2 and HT transmission modes are
selected. Four maintenance channels TmD(4:1)/
RmD(4:1) are available when the TX4 transmission
mode is selected.
In maintenance mode there is only one valid clock
TmCLK/RmCLK. The set of four signals TmD(4:1)
are collectively synchronised to the TmCLK clock
and the set of signals RmD(4:1) are collectively
synchronised with the RmCLK clock.
Input data appearing on the TmD 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 RmD outputs of the far-end
modem on the rising or falling edge of the RmCLK
clock depending on the setting of RESEL ( see Figure
1. 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.
The ACS406CS gives a choice between internally
and externally generated TmCLK clocks. When the
CKM pin is held Low, TmCLK is configured as an
output producing a clock at 16, 32 or 64kHz. 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
DR(5:1).
Whilst the TmD/RmD 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.
*For M4B = 1. For M4B = 0, 4 channels @ 1/4 TmCLK
Maintenance channel mode with Frame = 0
D D D D D
R R R R R
5 4 3 2 1
1 1 1 1 1
1 1 1 1 0
1 1 1 0 1
1 1 1 0 0
1 1 0 1 1
1 1 0 1 0
1 1 0 0 1
1 1 0 0 0
1 0 1 1 1
1 0 1 1 0
1 0 1 0 1
1 0 1 0 0
1 0 0 1 1
1 0 0 1 0
1 0 0 0 1
1 0 0 0 0
0 1 1 1 1
0 1 1 1 0
XTAL XTAL TmCLK Nos. of
(MHz) DC
33.792
31.560
32.768
30.88
32.768
30.88
32.768
30.88
32.768
32.768
32.768
32.768
32.768
32.768
16.384
15.440
32.768
30.88
528
493.125 64
512
482.5
512
482.5
512
482.5
512
512
512
512
512
512
512
482.5
512
482.5
(KHz)
64
64
64
64
64
64
64
64
64
64
64
64
64
32
32
64
64
Channels
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
1*
Table 20
10
Each DR(5:1) mode is designed to achieve a
particular communication frequency by the
combination of the XTAL value and Divide Constant
(DC) value. The recommended XTAL and the DC
value for each DR(5:1) selection are shown in Table
20.
If the recommended XTALs are not employed, then
the frequency of the TmCLK clock can be calculated
by dividing the XTAL frequency by the DC value.
Frame mode is selected when the input Frame = 1.
In Frame mode the channels TmD/RmD become
support channels to the main TPOS/TNEG data
channels and are associated with the TCLK and
RCLK clock rather than the TmCLK and RmCLK
clocks employed in maintenance mode.
Frame mode is only available for a subset of the
possible DR(5:1) settings; these are shown in Table
21. Where Table 21 denotes the number of Frame
channels available as zero, then the status of the
Frame input pin will be ignored and the support
channels will function in maintenance mode.
Data appearing on inputs TmD1/2 is latched into the
device on either the rising or falling edge of the
TCLK depending on the setting of TRSEL for both
internally and externally generated transmission
clocks.
Output data appearing on RmD1/2 is valid on the
rising or falling edge of the RCLK clock depending
on the setting of RESEL (see Figure 1. Timing
diagrams) .
Frame channel mode with Frame = 1
D D D D D XTAL
R R R R R (MHz) transitions Mode channels
5 4 3 2 1
1 1 1 1 1
1 1 1 1 0
1 1 1 0 1
1 1 1 0 0
1 1 0 1 1
1 1 0 1 0
1 1 0 0 1
1 1 0 0 0
1 0 1 1 1
1 0 1 1 0
1 0 1 0 1
1 0 1 0 0
1 0 0 1 1
1 0 0 1 0
1 0 0 0 1
1 0 0 0 0
0 1 1 1 1
0 1 1 1 0
33.792
31.560
32.768
30.88
32.768
30.88
32.768
30.88
32.768
32.768
32.768
32.768
32.768
32.768
16.384
15.440
32.768
30.88
TmD/TCLK Nos. of Frame
per period available
2/512
2/512
2/128
2/128
2/128
2/128
0
0
0
0
0
0
0
0
2/512
2/512
0
0
ACS406CS Issue 1.6 January 1999.
1
1
2
2
1
1
0
0
0
0
0
0
0
0
1
1
0
0
Table 21