Citizen Systems CBM-231 - Manual (Page 28)

CBM-230/231 User’s Manual
23 CITIZEN
7.3.2 Data Configuration
(1) (2) (3)
(1) Start bit
(2) Data bit(+ parity bit)
(3) Stop bit(1 or more)
(1) Start bit
When half a bit has passed since a fall edge of a mark to a space, the state of the bit is read in again, and if it
is a space, it will be recognized as a start bit. If it is a mark, it will not be recognized as the start bit. The
start bit will be detected again without assuming it to be an error.
(2) Data bit + parity bit
The data bit and parity bit are sampled for one bit worth of time since the time of half the start bit and
assume the then state to be the data for the relevant bits. The bits are arranged in order of bit 0, bit 1, ....,
parity bit, starting from the one next to the start bit.
(3) Stop bit
The stop bit is a 1-bit or more mark level. If a space is detected in detecting the stop bit, a framing error will
result.
7.3.3 Error Detection
A parity error, framing error, and overrun error are detected. When an error is detected, that data is stored in the
buffer as "?."
(1) Framing error
When a space is detected at stop bit detection time, an error result. That data is stored in the buffer as "?."