Citizen Systems iDP-3423 - Manual (Page 50)

iDP-3420/3421/3423 User’s Manual
50 CITIZEN
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t
Mark
b
0
, b
1
, b
2
, · · · ·
Space (1) (2) (3)
(1) Start Bit
(2) Data Bit (+ Parity Bit)
(3) Stop Bit (1 or More)
(1) Start bit
After a lapse of 1/2 bit from a mark-to-space fall edge, the state is read again, and if it is
a space, it is recognized as the start bit. If it is a mark, it is assumed neither the start
bit nor an error, and it is attempted to detect the start bit again.
(2) Data bit + parity bit
The data bit and parity bit are sampled for 1 bit worth of time from the 1/2 start bit.
The then state is assumed the data for the corresponding bit. A sequence of the bits are
named Bit 0, Bit 1, ..., parity bit, starting from the one closest to the start bit.
(3) Stop bit
The stop bit is a mark level of 1 bit or more. If a space is detected in detecting the stop
bit, a framing error results.