User`s guide

4-7

Programming over RS-232-C

Interface Capabilities

The baud rate, stop bits, parity, handshake protocol, and data bits must be

configured exactly the same for both the controller and the oscilloscope to

properly communicate over the RS-232-C bus. The oscilloscope’s RS-232-C

interface capabilities are as follows:

• Baud Rate: 9600, 19,200, 38,400, or 57,600

• Stop Bits: preset to 1

• Parity: preset to None

• Protocol: DTR or XON/XOFF

• Data Bits: preset to 8

Protocol

DTR (Data Terminal Ready) With a three-wire interface, selecting DTR for

the handshake protocol does not allow the sending or receiving device to control

data flow. No control over the data flow increases the possibility of missing data

or transferring incomplete data.

With an extended hardwire interface, selecting DTR allows a hardware

handshake to occur. With hardware handshake, hardware signals control data

flow.

XON/XOFF XON/XOFF stands for Transmit On/Transmit Off. With this mode

the receiver (controller or oscilloscope) controls data flow and can request that

the sender (oscilloscope or controller) stop data flow. By sending XOFF (ASCII

17) over its transmit data line, the receiver requests that the sender disables

data transmission. A subsequent XON (ASCII 19) allows the sending device to

resume data transmission.

A controller sending data to the oscilloscope should send no more than 32 bytes

of data after an XOFF.

The oscilloscope will not send any data after an XOFF is received until an XON

is received.

Data Bits

Data bits are the number of bits sent and received per character that represent

the binary code of that character.

Information is stored in bytes (8 bits at a time) in the oscilloscope. Data can be

sent and received just as it is stored, without the need to convert the data.