1-4
1
1.4
IEEE 488 INTERFACE
1.4.1 488.1 Capabilities
The N4865A's 488 Bus interface meets the IEEE STD 488.1-1987 standard
and has the following capabilities:
SH1, AH1, T6, L4, SR1, PP0, DC0, RL0, DT0, C1 - C4 and C9
The N4865A's GPIB Bus drivers incorporate powerup/down protection to
prevent sending invalid data to the bus. GPIB fanout is up to 14 devices.
1.4.2 GPIB Addresses
The N4865A's GPIB primary address is entered and saved in fl ash memory
when the unit is confi gured. Confi guring is done via the N4865A's Ethernet
Interface.
Primary address range is 0 - 30. The default GPIB address is 4.
1.4.3 Conversion Operation
The N4865A follows the IEEE-488.2 Message Exchange Protocol when han-
dling GPIB commands and device messages.
1.4.4 Device Messages
All device data messages sent to the N4865A must be terminated with EOI
asserted on the last character. The N4865A sends data received from the
GPIB bus to the companion oscilloscope with a
device_write
RPC. When the
N4865A is addressed to talk, it sends a
device_read
RPC to the companion
device_read
device_read
oscilloscope to read the expected reply. The N4865A will assert EOI when it
outputs the last character of the received response if the END bit was asserted
in the
device_read
response packet.
device_read
device_read
Large Listen messages are handled by holding off the GPIB bus while a buffer
of data is transferred to the oscilloscope. Large data responses are processed by
reading multiple talk buffers worth of data from the oscilloscope and outputting
them to the GPIB bus until a response packet is received from the oscilloscope
with the END bit asserted.
GPIB Listen buffer
1024 bytes (see Note 1)
GPIB Talk buffer
1024 bytes (see Note 1)
Note 1. Working buffer size may be smaller if the companion oscilloscope reports smaller maximum
packet sizes in its
create_link
response.
create_link
create_link
Summary of Contents for N4865A
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