IOtech Digital488, Manual

Page: 31 / 64

3-10, Command Descriptions
7-17-01
Digital488 User’s Manual
Port Pn
The Port command determines which port is selected for data input/output. In the default mode ( P0 ),
all ports are selected. The P1 thru P5 commands select a specific eight-bit port.
It is recommend that the Bus Output command be used with the PO mode to determine which ports will
be output when the Digital488 is addressed to talk. Data in modes P1 through P5 will be input or output
in-groups of eight bits.
P0 All five ports are selected
P1
Port 1 is selected
P2 Port 2 is selected
P3 Port 3 is selected
P4 Port 4 is selected
P5
Port 5 is selected
Example:
CLEAR 718 reset the Digital488
OUTPUT 718;"P4X" select port 4
Service Request Mask (SRQ) Mn
The Service Request (SRQ) mode is used by the Digital488 to alert the controller to one of several
conditions described below. Multiple SRQ conditions can be enabled simultaneously by issuing them
separately or by combining them in one command. If multiple SRQ commands are contained within the
same command string, each SRQ command should be followed by an Execute command (X).
The programmed SRQ modes will remain enabled until the M0 command is sent, or the controller sends
a Device Clear (DCL), Selected Device Clear (SDC), or Interface Clear (IFC) command.
M0
SRQ is disabled
M1 SRQ on Service input transition
M2 SRQ on EDR input transition
M4 SRQ on bus error
M8 SRQ on Self-Test error
M16 SRQ on Ready
MO default mode disables the SRQ function, preventing the Digital488 from generating a Service Request.
M1 will generate a Service Request when the Service Input line makes a transition. Refer to the Invert
command (I64) description for programming the polarity of the Service input line.
M2 will generate a Service Request when the EDR input makes a transition. Refer to the Invert command
(I32) description for programming the polarity of the EDR input line.
M4 will generate a Service Request when a bus error occurs. The most common bus error is sending an
invalid command to the
Digital488 . For example, attempting to select an 'F6' format when no 'F6' format
exists will generate a Service Request when the M4 mode is selected.