Spectrum Brands MC.31XX - Manual (Page 60)

60 MC.31xx Manual
External clocking Clock generation
External clocking
Direct external clock
An external clock can be fed in on the external clock connector of the board. This can be any clock, that matches the specification of the
card. The external clock signal can be used to synchronize the card on a system clock or to feed in an exact matching sample rate.
The maximum values for the external clock is board dependant and shown in the table below.
Termination of the clock input
If the external connector is used as an input, either for feeding in an external reference clock or for external clocking you can enable a 50
Ohm termination on the board. If the termination is disabled, the impedance is high. Please make sure that your source is capable of driving
that current and that it still fulfills the clock input specification as given in the technical data section.
Minimum external sample rate
The minimum external sample rate is limited on all boards to 1 kHz and the maximum sample rate depends on the specific type of board.
The maximum sample rates for your type of board are shown in the tables below.
Maximum external samplerate in MS/s
An external sample rate above the mentioned maximum can cause damage to the board.
Ranges for external sample rate
Due to the internal structure of the board it is essential to know for the driver in which clock range the external clock is operating. The external
range register must be set according to the clock that is fed in externally.
The range must not be left by more than 5 % when the board is running. Remember that the ranges depend
on the activated channels as well, so a different board setup for external clocking must always include the
related clock ranges.
This table below shows the ranges that are defined by the different range registers mentioned above. The range depends on the activated
channels and the mode the board is used in. Please be sure to select the correct range. Otherwise it is possible that the board will not run
properly.
Register Value Direction Description
SPC_EXTERNALCLOCK 20100 read/write Enables the external clock input. If external clock input is disabled, internal clock will be used.
Register Value Direction Description
SPC_CLOCK50OHM 20120 read/write A „1“ enables the 50 Ohm termination at the external clock connector. Only possible, when using
the external connector as an input.
Remapped channels
31
10
31
11
31
12
31
20
31
21
31
22
31
30
31
31
31
32
31
40
ch0 ch1 ch2 ch3 ch4 ch5 ch6 ch7
x 1 1 1 10 10 10 25 25 25 50
x x 1 1 1 10 10 10 25 25 25 25
x x n.a. n.a. 1 n.a. n.a. 10 n.a. n.a. 25 n.a.
x x x x n.a. n.a. 1 n.a. n.a. 10 n.a. n.a. 25 n.a.
x x x x n.a. 1 1 n.a. 10 10 n.a. 25 25 n.a.
x x x x x x x x n.a. n.a. 1 n.a. n.a. 10 n.a. n.a. 25 n.a.
Register Value Direction Description
SPC_EXTERNRANGE 20130 r/w Defines the range of the actual fed in external clock. Use one of the below mentioned ranges
EXRANGE_SINGLE 2 External Range Single
EXRANGE_BURST_S 4 External Range Burst S
EXRANGE_BURST_M 8 External Range Burst M
EXRANGE_BURST_L 16 External Range Burst X
EXRANGE_BURST_XL 32 External Range Burst XL