SECTION 15.6 ERROR CHECKING.
The data has two checking systems to ensure accuracy. The Longitudinal Redundancy Check (LRC) and the Parity
check. They can be set to odd or even.
Even Parity makes the number of 1‟s in the data being checked total an even number (2,4,6…)
Odd Parity makes the number of 1‟s in the data being checked total an odd number (1,3,5…)
If 123 was encoded in 5 MPC on Track 2 with ODD Parity and EVEN LRC would look thus:
II0I0 I0000 0I000 II00I IIIII 00I0I
; 1 2 3 ? LRC
The first 4 bits of each group (except the LRC) represent the information ( 2 = 0I00 )
The 5
th
bit of each group (except the LRC) is the parity bit for it‟s group ( 0 or I )
The LRC consist of a parity bit for all of the information groups (each bit in the LRC is the parity bit for the same coloured
bits in all the other groups).
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