PPC3™ OPERATION AND MAINTENANCE MANUAL
© 2002-2007 DH Instruments, a Fluke Company Page 82
4.2.1.2 IEEE-488
The PPC3 IEEE-488 interface is located on the back of the unit. The physical
and electrical interface conforms to IEEE Std 488.1-1987 Subset E2 and IEEE
Std. 488.2-1992. You should not attempt to communicate with the IEEE-488
interface while using the COM1 interface. The IEEE-488 receive buffer is
250 bytes deep. If you attempt to overflow the buffer, the PPC3 will hold off
release of the NRFD handshake line until it can service and empty the receive
buffer. This keeps the buffer from overflowing. It is recommended that you use
the query form for all remote commands and wait for a reply to each command to
ensue proper operation and order of command execution.
4.2.1.3 COM2
The PPC3 COM2 RS232 interface is located on the back of the unit. Its most
common use is to connect to DHI RPM4 reference pressure monitors to PPC3 to
add external measurement devices to the PPC3 system (see Section 3.2.4)
COM2 can be used to allow the host computer to communicate with another
device through the PPC3. This allows the user to use one host COM port to
communicate with the PPC3 and an additional RS232 device. Refer to the “#”
and “PASSTHRU” remote program commands for details.
COM2 is a 9-pin female DB-9F connector configured as a DTE device. Data is
transmitted out of the unit using pin 3, and is received on pin 2. This allows a normal
pin-to-pin DB-9M to DB-9F RS232 cable to be used to connect to a DCE device.
Handshaking is not required or supported.
Table 15. COM2 DB-9F Pin Designations
PIN # FUNCTION DESCRIPTION
2 RxD This pin transmits serial data from the PPC3 to a device.
3 TxD This pin accepts serial data from the external device.
4 DTR This pin is Data Terminal Ready (DTR) (held at + 5 V).
5 Grn This pin is the common return for the TxD and RxD signals.
4.3 PROGRAMMING FORMATS
PPC3 supports two program message formats, the “classic” and “enhanced” formats. The user must
select which format to use. Selection can be accomplished from the front panel (see Section
3.5.2.3) or
remotely using the “MSGFMT” program message (see Section 4.4.4).
The main difference between the two formats is that when using the IEEE-488 interface, a “?” must be
included in an enhanced command for there to be a response from the PPC3. In all other cases (classic or
enhanced), every command has a response. In addition, the enhanced message format supports IEEE Std
488.2 syntax, format and status reporting.
The default is the classic format to allow downward compatibility with existing host software.
In either format, it is recommended that you start out a command sequence with the “*CLS” command,
which clears all of the communication and error queues. The basic commands are similar for both the
classic and enhanced formats, but the usage, syntax, format and status reporting are different.
The PPC3 program message set is downward compatible with the previous PPC2 and PPC2+ program
message set. Some PPC2 and PPC2+ commands are not fully supported due to functional differences
between PPC3 and earlier products.
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