IOtech Digital488OEM - Data Ready Rn; End or Identify (EOI) Kn

3-4, Command Descriptions 7-17-01 Digital488 User’s Manual
Data Ready Rn
The Data Ready command enables digital input data to be latched. When used in conjunction with the
Service Request (M2) command, the External Data Ready line can both latch the input data and signal
the controller that new data is available.
In the default mode, (R0) data is read when the Digital488 is addressed to talk. In the R1 mode, it will wait
for the selected External Data Ready (EDR) transition before reading the data and formatting it for
output. If the Digital488 is addressed to talk before EDR is asserted, the bus will hang up until the EDR
pulse occurs. Once EDR is asserted, the data will remain latched until the interface is addressed to talk and
the data is read by the controller. If EDR transitions again before the previous EDR buffered data has been
output, the Digital488 will generate an EDR Overrun error and ignore the EDR read request.
After output in the F0 through F4 formats, the Digital488
must be re-addressed to talk to perform
subsequent buffered output of EDR captured data. EDR
cannot be used to capture data
in the F5 high-speed binary format
The EDR signal must be at least 1 microsecond wide and should have a rise and fall time of less than 1.0
microsecond. The EDR line defaults to rising-edge sensitive but can be changed to falling-edge sensitive
with the Invert command (I32).
R0
Data is not latched, and is read whenever the Digital488
is addressed to talk
R1
Data is latched on an EDR transition
Example:
CLEAR 718
reset the Digital488
OUTPUT 718;"R1X"
data is only read after a rising-edge
signal is applied to the EDR
line
End or Identify (EOI) Kn
The EOI line is one of five interface management lines on the IEEE 488 Bus. It is used by a talker
to indicate the end of a multiple byte transfer sequence. At power-on, the setting of Switch S1 determines
the default EOI mode. The controller can change the EOI mode by programming the Digital488 from
the bus. In the K0 mode, the EOI line is asserted by the Digital488 on the last byte of every bus output
string. In the K1 mode the EOI function is disabled (except when using the binary modes [F4 and F5]).
K0
EOI enabled, assert EOI on last byte transferred
K1
EOI disabled, do not assert EOI on last byte transferred
Example:
OUTPUT 718;"K1X"
disables EOI on last byte