Specifications

B-4

Appendix B

Pattern Editor and Subrate Data

If you select a mark density, zerosub or user pattern (all RAM patterns) using the pattern

editor, the pattern present at the parallel data out ports depends on pattern length and the

trigger bit position.

The following paragraphs explain how pattern length and trigger bit position effect the

subrate data patterns output from the parallel data ports.

Pattern Lengths Divisible By Four

On a pattern whose length is a multiple of four, and with the trigger bit position set to

bit 0, the subrate channel correspondence is as follows:

Pattern xxxxxxxxx

Subrate Channel D0 D1 D2 D3 D0 D1 D2 D3 D0

The following example shows a 20-bit pattern with the pattern trigger bit position set to

bit 0.

11110000100001001010

D010101

D110010

D2 10001

D3 10000

Pattern Lengths Not Divisible By Four

To determine the pattern present at the parallel data out ports, the pattern length must be

multiplied up until it is a multiple of 4 (some patterns as much as 256 times) and then

every fourth bit assigned to D0 to D3. All odd-length patterns are replicated 256 times.

Subrate Output Pattern Change with Trigger Bit Position

Note that changing the trigger bit position changes the subrate channel correspondence

and hence the pattern output from the parallel data out ports. For example, if the trigger

position is set to bit 1 then the output is as follows:

Pattern xxxxxxxxx

Subrate Channel D3 D0 D1 D2 D3 D0 D1 D2 D3