Keysight 34959A, Руководство пользователя

Страница: 30 / 39

30 Keysight 34959A User’s Guide
SCPI commands described in the previous section, “Analog Bus Relay Functions”
on page 28, also apply to these relay drives. Since relay selection is left to the
user’s discretion, take particular note of the maximum current limits specified in
the Electrical Specifications table on page 22 when choosing and driving your
relays.
Digital I/O Functions
The Digital input/output (DIO) interface provides two 8-bit bytes of DIO, which
may be accessed individually or combined together to form one 16-bit word.
Three control lines are provided. See the Pin Connection Information table (for
P102) on page 14 for connection information. The three control lines provide
handshake of the read/write SCPI commands (
SENSe
and
SOURce
) sent to the
mainframe, as follows:
Timing for Read Commands
When the 34980A receives a SCPI command to read from the breadboard, control
line 3 is set high (its default setting, indicating a read request).
If the read target is byte 1 , control line 1 is set strobe low, the byte 1 data is read,
and then control line 1 is set strobe high. The strobe pulse width is 3.75
μ
s, and
the time from strobe low to valid data is 1.25
μ
s.
Similarly, if the read target is byte 2 , control line 2 is set strobe low, the byte 2
data is read, and then control line 2 is set strobe high. The strobe pulse width is
3.75 μ s, and the time from strobe low to valid data is 1.25 μ s.
If both bytes are configured as a word, and targeted as a word in the read (
SENSe
)
command , both control lines 1 and 2 are set strobe low, all 16 bits are read, and
then both control lines are set strobe high. The strobe pulse width is longer (5
μ
s)
than for a single byte read, but the time from strobe low to valid data is still 1.25
μ
s.
In all three cases, once the data has been read by the mainframe, the data lines
are left in tri-state (indeterminate).
The read timing diagram is shown on
page 32 .
Timing for Write Commands
When the 34980A receives a SCPI command to write to the breadboard, control
line 3 is set low (indicating a write request).