Cisco Systems DS Series, DS71-MD4 manual Stop Bits, Parity

DS71-MD4 Serial host and 56k Modem

"	5	"	1
"	6	"	2
"	7	"	3
"	8	"	4

Enter Select :

Stop Bits

The Stop Bits are used to signal the end of communication for a single packet. Since the data is clocked across the lines and each device has its own clock, it is possible for the two devices to become slightly out of sync. Therefore, the stop bits not only indicate the end of transmission but also give the computers some room for error in the clock speeds. The more bits that are used for stop bits, the greater the lenience in synchronizing the different clocks, but the slower the data transmission rate.

Select “Stop Bits” the DS displays the following: Default is 1.

"1 " ......1

"2 " ......2

Enter Select :

Parity

Parity is a simple form of error checking used in serial communication. For even and odd parity, the serial port will set the parity bit (the last bit after the data bits) to a value to ensure that the transmission has an even or odd number of logic high bits. For example, if the data was 011, then for even parity, the parity bit would be 0 to keep the number of logic high bits even. If the parity was odd, then the parity bit would be 1, resulting in 3 logic high bits. This allows the receiving device to know the state of a bit so as to enable the device to determine if noise is corrupting the data or if the transmitting and receiving devices' clocks are out of sync.

With no parity selected, it's assumed that there are other forms of checking that will detect any errors in transmission. No parity also usually means that the parity bit can be used for data, speeding up transmission. In modem-to-modem communication, the type of parity is coordinated by the sending and receiving modems before the transmission takes place.

Select “Parity” the DS displays the following: Default is None.

" None "			1
"	Even	"	2
"	Odd	"	3
	Enter Select :

XON/XOFF

For a simple communication between modems three connected lines are needed: TX, Rx, and Ground. For the data to be transmitted, both sides have to be clocking the data at the same baud rate. While this method is sufficient for most applications, it is limited in being able to respond to problems such as the receiver getting overloaded. This is where serial handshaking can help. XON/XOFF is software data flow communications protocol for controlling the flow of data between Baytech and other devices. Baytech units will send an XOFF character when it can't take any more data and when it can once again take more data, will send an XON character to the transmitter.

Select “Xon/Xoff” the DS displays the following, Default is Off:

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