Msi Code (Variant Of Plessey); Plessey - Intermec CK30 Programmer's Manual

Plessey

MSI Code (Variant of Plessey)

™
TE 2000 3270 Terminal Emulation Programmer's Guide
Plessey finds its origin in the pulse width modulated (PWM) code devel-
oped in England. It is widely used for shelf markings in grocery stores.
Pulse width modulated codes represent each bit of information by a bar
and space pair. A zero bit consists of a narrow bar followed by a wide
space, while a one bit consists of a wide bar followed by a narrow space. It
is mainly a numeric symbology (0–9) with six extra characters available for
assigning any symbol or letter desired.
Plessey codes are not self-checking and employ a variety of check charac-
ters. Plessey employs a polynomial-based Cyclic Redundancy Check
(CRC). For start and stop characters, Plessey employs a 1101 and pre-
viously used a 0101.
This symbology is very limited about what information can be encoded. It
is not considered for new applications.
In addition to Plessey characteristics, the MSI Code employs a Modulus
10 Check. For start and stop checks, MSI employs a single bit pair of 1 as
a start symbol and a single bit pair of 0 as a stop symbol. MSI reverses the
1-2-4-8 BCD pattern for bit pair weighting to 8-6-2-1.
—
Appendix B Bar Code Symbologies
327