Ultra Electronics Ltd
Pronto Maintenance Manual
- 63 -
SECTION 14.6
ERROR CHECKING.
The data has two checking systems to ensure accuracy. The Longitudinal Redundancy Check and the Parity check.
They can be set to odd or even.
Even Parity
makes the number of I’s in the data being checked total an even number (2,4,6…).
Odd Parity
makes the number of I’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 its 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).
