488 CONTROLLER
84
7.6.3 D
EVICE
C
LEAR
(DCL
AND
SDC)
Device Clear resets the 488 Controller’s IEEE input and serial input buffers. Any pending data and Service
Requests (SRQ), including the information they convey, are lost. In addition, the X-ON serial control
character is transmitted if X-ON/X-OFF is enabled.
7.6.4 I
NTERFACE
C
LEAR
(IFC)
IFC places the 488 Controller in the Talker/Listener Idle State. It clears any pending requests for service
(SRQ). The condition which caused the SRQ remains unmodified.
7.6.5 S
ERIAL
P
OLL
E
NABLE
(SPE)
When Serial Poll Enabled, the 488 Controller sets itself to respond to a serial poll with its serial-poll status
byte if addressed to talk. When the serial poll byte is accepted by the controller, any pending SRQs are
cleared. The 488 Controller will continue to try to output its serial-poll response until it is “Serial Poll
Disabled” by the controller.
7.6.6 S
ERIAL
P
OLL
D
ISABLE
(SPD)
Disables the 488 Controller from responding to serial polls by the controller.
7.6.7 U
NLISTEN
(UNL)
UNL places the 488 Controller in the Listener Idle State.
7.6.8 U
NTALK
(UNT)
UNT places the 488 Controller in the Talker Idle State.
7.7 IEEE Address Selection
SW3-1 through SW3-5 select the IEEE bus address of the 488 Controller when in the Peripheral Pass-Thru
mode. The address is selected by simple binary weighting, with SW3-1 being the least significant bit and
SW3-5 the most significant. The following figure shows the IEEE address of the 488 Controller set to 10.
Figure 7-3. SW3 view for IEEE address selection.
L
ISTEN
O
NLY
M
ODE
Listen Only is a special type of Peripheral operation. In the Listen Only mode the 488 Controller accepts all
data transmitted on the bus and transfers it out its serial port. The 488 Controller is set to Listen Only mode
by setting its address to 31 (switches SW3-1 through SW3-5 all open).
