KEPCO BIT 232F - Manual (Page 23)

BIT 232 022800 4-1
SECTION 4 - OPERATION
4.1 GENERAL
The Kepco BOP Power Supply, with an installed BIT 232/BIT 232-F Interface Card, may be pro-
grammed over the RS232C bus using either SCPI (Standard Commands for Programmable
Instruments) or CIIL (Control Interface Intermediate Language) commands. SCPI and CIIL pro-
vide a common language used in an automatic test system. (Refer to Table 2-3 for input/output
signal allocations.)
4.2 RS232-C BUS PROTOCOL
The BIT Card may be operated via an RS232-C terminal, or from a PC using a terminal emula-
tion program. The following settings must be observed:
• Baud rate: 9600
• Parity: None
• Data Bits 8
• Stop Bits 1
The above settings are established by the firmware and cannot be changed by the user
although firmware with alternate settings can be ordered. It is recommended that the user pro-
gram the computer’s serial interface to match the above setting. Refer to PAR. 2.5 for RS232
connections.
4.3 RS232 IMPLEMENTATION
The following paragraphs are provided to help the user understand how the RS232 interface is
implemented in the BIT 232 and BIT 232-F Interface Cards. Since the RS232 protocol does not
use a parity bit, the echo method is used to ensure reliable communication between the com-
mand originator (computer) and the BIT Card, thus avoiding a more complex “handshake” pro-
tocol.
When a character is received through the RS232 Interface, the software checks for the back-
space character, hex value 08 (08
H
). If the backspace character is not detected, the received
character is put in a buffer, the buffer pointer is incremented, and it is sent (echoed) back to the
originator. If the backspace character is detected, the buffer pointer is decremented, and three
characters are sent to the originator: Backspace (08
H
), Blank (20
H
), and Backspace (08
H
).
These three characters permit a direct interface with a terminal emulation program, effectively
erasing the last character.
When either a Carriage Return, CR, (0D
H
decimal value 13, 13
10
) or Line Feed, LF, (0A
H
, 10
10
)
is received by the BIT Card, the buffer contents are transferred to the SCPI (PAR.4.4) or CIIL
(PAR. 4.5) parser for analysis and execution of command(s). If the command requires the power
supply to respond, the response message is immediately returned to the command originator
via the RS232 interface.
To inform the command originator that the parsing and execution phases are complete, the BIT
Card returns the following three characters: CR, LF, and > (3E
H
, 62
10
). These characters create
the “prompt” effect if a terminal emulation program is the command(s) originator.