Citizen Systems 291, CBM-290 user manual Date configuration, Error detection

CBM-290/291 User’s Manual

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.

7.4Error 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 "?".

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