Operator Manual Firmware Ver.3.05 and higher Instruction Manual

3-32 BOP-1K-GL 022814
The CAN character resets the receive and transmit pointers and queues.
CAUTION: When the serial port has received an XOFF, the error message -400, QUE
error will be placed in the queue to indicate the loss of transmitted informa-
tion due to a received XOFF character. When XON is received, the unit will
transmit all data in it's buffer followed by the exclamation character (!). This
(!) character is not part of any message from the BOP and indicates the
transmission buffer has been cleared and the BOP is idle.
All non-control characters are sent via the serial port of the command originator. The control
character BS is echoed as BS Space BS. Only the first control character is returned in response
to either a CR LF or LF CR character sequence (see Figure 3-8).
3.6.4.2.1 XON XOFF METHOD
The XON XOFF method allows the BOP to control when the command originator is allowed to
send data. The command originator can only send data after the XON (transmission on) charac-
ter (011
H
) has been received; the command originator stops sending data after receiving the
XOFF (transmission off) character (013
H
), and waits until the XON character is received before
sending additional data.
Control characters, either CR or LF, are returned as XOFF CR if echo mode is on, and as XOFF
if echo mode is off. XOFF stops data from the command originator and the BOP returns the nor-
mal sequence of CR LF (if echo mode is enabled).
3.6.4.2.2 ECHO MODE
Echo mode is one method of ensuring data is transferred without errors. This mode should only
be enabled when errors in operation are detected.
Each byte (character) is echoed back to the sender where it is verified as the same character
that was just sent. If the wrong character is echoed back, sending the ESC character clears the
line to allow retransmission of the character. It is important the CR and LF characters are NOT
sent until the verification process is complete.
When working in echo mode, it is possible to receive the NAK (15 hex) from the BOP. This indi-
cates an unknown quantity of echoed characters have been lost due to a queue overflow prob-
lem. The error queue will also contain the -400, QUE error message, To prevent this, please
insure the received data string does not exceed 127 characters between line terminators and no
more than four queries are sent between line terminators in SCPI mode of operation
All non-control characters are sent via the serial port of the command originator.
3.6.4.2.3 PROMPT METHOD
The command originator sends a message line (command) to the BOP and waits until the
prompt sequence CR LF > (3E
H
, 62
10
) is received. The BOP sends the prompt sequence
CR LF > to the command originator indicating the power supply is ready to receive the next
command and data will not be lost. This method is useful in an interactive mode as well as with
certain process controllers.