Citizen Systems 291 - Manual (Page 35)

CBM-290/291 User’s Manual
21 CITIZEN
7.3 Date configuration
1 Start bit
2 Data bit (+ parity bit)
3 Stop bit ( 1 or more )
(1) Start Bit
In 1/2 bit from the mark-to-space starting edge, state is read once again. When "space" state is confirmed,
it is recognized as the start bit. If it is "mark" state, it is not taken as the start bit. Without taking it as an
error, detection of a start bit is carried out once again.
(2) Data Bit + Parity Bit
Data bit and parity bit are sampled at 1/2 start bit for time length equal to 1 bit. The state thus sampled is
taken as the data for the bit concerned. Bits are named as Bit 0, Bit 1, ..... parity bit counted from the one
close to the start bit.
(3) Stop Bit
The stop bit is a mark level of 1 bit or more. With "space" having been detected on detection of a stop bit,
framing error takes place.
7.4 Error detection
Parity, framing, and overrun are detected. On detection of any error, the data are stored in the buffer as "?".
(1) Framing Error
With "space" state having been detected on detection of a stop bit, error takes place. The data are stored in
the buffer as "?".
(2) Parity Error
With an error having been detected under specifying parity check, the data is stored in the buffer as "?".
(3) Overrun Error
On detection of an overrun error, the data are stored in the buffer as "?".