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3-8, Command Descriptions

7-17-01

Digital488 User’s Manual

Data received for output to the digital ports must be contained within a prefix (

) and a suffix (

If the amount of data sent is less than the number of bits programmed as outputs, the least-significant bits
will contain the data sent and the most-significant bits will be cleared to logic zero. If the data sent
is greater than the number of bits programmed for output or selected by the

command, the

Digital488

will generate a conflict error and ignore the entire command string. The

Data Strobe

output is pulse for

approximately 50 microseconds after new data is output on the selected port(s).

When the

Digital488

is addressed to talk (

) it asserts

Inhibit

, reads the data from all ports, unasserts

Inhibit

and outputs the number of characters determined by the

and

commands. Leading zeros

are not suppressed and the bus terminators are appended to the output. After output, the

Digital488

must

be re-addressed to talk to perform subsequent reads.

EDR

(

) may also be used to capture data in this

format.

Example:

OUTPUT 718;"F3X"

select decimal mode

ENTER 718; A$

read data from the

Digital488

DISP A$

display shows

240;165

OUTPUT 718;D100;200ZX

output

100 & 200

to the

Digital488

ENTER 718; A$

read data from the

Digital488

DISP A$

display shows

100;200

F4 Format - Binary

In the F4 binary format, no error checking is performed and caution must be exercised when using this
mode to avoid locking the IEEE bus.

When addressed to listen, the

Digital488

expects the "D" prefix followed by five bytes of data beginning

with PORT5 without the "Z" suffix. If any digital I/O port is configured as input, the data to that input port
will be ignored.

When the

Digital488

is addressed to talk (R0) it asserts Inhibit, reads the data from all ports, unasserts

Inhibit and outputs 5 bytes beginning with PORT5 with EOI asserted on the last bye. Bus terminators, with
the exception of EOI, are not appended to the output. After output, the

Digital488

must be re-addressed

to talk to perform subsequent reads. EDR (R1) may also be used to capture data in this format.

F5 Format - High Speed Binary

In the

high-speed binary format, the command interpreter is disabled. When addressed to listen,

the

Digital488

treats all bytes received as data to be output to the Digital I/O ports. Each time it receives

five bytes

detects EOI asserted, it pulses the

Data Strobe

for approximately 15 microseconds.

Data is expected in a PORT5, PORT4, PORT3, PORT2, PORT1 sequence. If only two bytes are received,
with EOI asserted on the second byte, the

Digital488

will update PORT5 with the first byte received

PORT4 with the second and pulse the

Data Strobe

. Since the interface treats all received characters

as data, the

command will not be recognized.

To place the

Digital488

in the

format, the 3-character string "

F5X

" should be the last command sent

to the interface

without

terminators. Any characters appended to this command, such as carriage return

or line feed, will be considered data and the output ports will reflect those character values.

When addressed to talk in this format, it asserts

Inhibit

, reads the data from all ports, unasserts

Inhibit

and

outputs the binary data to the bus with EOI asserted on the fifth byte. When the last data byte is transferred,
the data is read again in anticipation of another data transfer. If

Inhibit

is used to sequence external

hardware, this line will pulse N+1 times; where N is the number of total (5 byte) data transfers.
In this format, the

Digital488

does

not

have to be re-addressed to talk to read the ports multiple times.

EDR

cannot be used to capture data in the

high-speed binary format.

The only programmable method to exit the

high-speed binary format is device clear (