42 Understanding the Agilent E1330B Digital I/O Module
Chapter 4
The FLG Line
(Input)
Each port has a flag (FLG) line. A flag line is an input line from a peripheral
and has two states: READY and BUSY. A flag line is normally used in
conjunction with the corresponding control line (CTL) to establish a
handshake between a peripheral and the Digital I/O Module. SCPI
commands that define handshake modes typically use the FLG and CTL
lines. The state of the FLG line can also be read with a SCPI command to
implement custom handshakes. Positive polarity is the default. The
following shows the effect of changing the polarity of the FLG line.
The CTL Line
(Output)
Each port has a control line (CTL). A control line is an open collector output
line from the Digital I/O module to the peripheral and has two states: TRUE
and FALSE. A control line is normally used in conjunction with the
corresponding flag line on the same port to establish a handshake between a
peripheral and the Digital I/O Module. SCPI commands that define
handshake modes typically use the FLG and CTL lines. The state of the CTL
line can be read and set with SCPI commands to implement custom
handshakes. Positive polarity is the default. The following shows the effect
of changing the polarity of the CTL line.
The I/O Line
(Output)
Each port has an open collector I/O line which is output from the Digital I/O
module to the peripheral and has two states: TRUE or FALSE. The state of
the I/O line is not directly programmable.
When the I/O line is:
TTL High = TRUE = 1 = Input
The data transceiver of that port is enabled for input. The peripheral may
respond to the signal by enabling itself to send data.
When the I/O line is:
TTL Low = FALSE = 0 = Output
The data transceiver of that port is enabled for output. The peripheral should
respond to the signal by enabling itself to receive data.
Caution
To prevent damage to the Digital I/O module, when the I/O line is
set for Output (TTL Low), the peripheral MUST NOT attempt to
source on any data lines.
POSitive Polarity
TTL High = BUSY = 1
TTL Low = READY = 0
NEGative Polarity
TTL High = READY = 0
TTL Low = BUSY = 1
POSitive Polarity
TTL High = TRUE = ON = 1
TTL Low = FALSE = OFF = 0
NEGative Polarity
TTL High = FALSE = OFF = 0
TTL Low = TRUE = ON = 1
Содержание E1330B
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