Citizen Systems CBM-270 user manual Error Detection, Output TXD, DTR Printer Side Host Side

CBM-270 User’s Manual

(2)Data bits + Parity bit

The system samples the data bits and parity bit for the 1 bit worth of time from 1/2 start bit and assumes the then status as the data for the relevant bits. The bits are called Bit 0, Bit 1, ..., Parity bit, counting from the one closest to the start bit.

(3)Stop bit

The stop bit is the Mark level of 1 bit or more. If a space is detected in detecting the stop bit, a framing error will result.

7.3.3Error Detection

The system detects a parity, framing, or overrun error. If an error is detected, the relevant data will be stored in the buffer as "?".

(1)Parity error

With a parity check specified, if an error is detected at parity check time, the relevant data will be stored in the buffer as "?".

(2)Framing error

This error results if the Space status is detected at stop bit detection time. The relevant data will be stored in the buffer as "?".

(3)Overrun error

If an overrun error is detected, the relevant data will be stored in the buffer as "?".

7.3.4Data Receiving Control

If DTR/DSR control has been selected, the data from the host side will be received when the BUSY signal is at "Low," but not received when at "High." If DTR/DSR has not been selected, the data from the host side will be received after sending XON, but not after sending XOFF.

7.3.5Buffering

To transfer the data to the input buffer, there are two control signals available: DTR signal and TXD signal. The host side is immediately freed, since the data can be buffered up to 2 KB.

(1)DTR signal (See 7.3.1-(2))

(2)TXD signal (See 7.3.1-(3))

7.3.6Electrical Characteristics RS-232C Circuit

Input (RXD, DSR)

[Printer Side] [Host Side]

RXD

Mark=(-8V): Stop bit

Space=(+8V): Start bit

Equivalent MAX232

Output (TXD, DTR)

[Printer Side] [Host Side]

DTR

Equivalent to MAX232
Mark=(-8V): At Busy
Space=(+8V): At Busy	TXD

Mark=(-8V): 1

Space=(+8V): 0