83
DIO2
Serial Handshake
This bit indicates the present state of the serial handshake. If it is set to “1,” the serial device
connected to the 488 Controller is capable of accepting serial data. If it is set to “0,” the RTS
line is unasserted, if the 488 Controller is configured for hardware handshake, or the X-OFF
character has been received, if the 488 Controller is configured for X-ON/X-OFF software
handshake.
DIO1
Not Used—Always “0”
7.5 Use of Serial and Bus Terminators
The 488 Controller can be configured to provide serial-to-IEEE-488 and IEEE-488-to-serial terminator
substitution. This is useful when interfacing a serial device that only issues carriage return [CR] as an
output terminator to an IEEE controller that expects a carriage return followed by a line feed [CR-LF].
In this previous case, the serial terminator should be selected for CR Only while the IEEE terminator is set to
CR-LF. When a serial CR character is received, it is discarded and replaced with an IEEE CR followed by an
IEEE LF. In the IEEE-to-serial direction, the IEEE CR is unconditionally discarded. Upon receipt of the IEEE
LF, a serial CR is substituted.
The 488 Controller can be made totally data-transparent by setting both the serial and IEEE terminators to
be CR Only or LF Only. To decide which terminators are appropriate, see the instruction manuals for the
serial device and the IEEE controller. For selection of the 488 Controller’s serial and bus terminators, refer
to
Chapter 3
.
7.6 IEEE 488 Bus Implementation
As a pass-thru bus peripheral, the 488 Controller implements many of the capabilities defined by the IEEE
488 1978 specification. These are discussed in the following subsections. The 488 Controller does not
support or respond to these bus uniline and multiline commands:
Remote Enable (REN)
Go to Local (GTL)
Group Execute Trigger (GET)
Local Lockout (LLO)
Take Control (TCT)
Parallel Poll (PP)
Parallel Poll Configure (PPC)
Parallel Poll Unconfigure (PPU)
Parallel Poll Disable (PPD)
7.6.1 M
Y
T
ALK
A
DDRESS
(MTA)
When the 488 Controller is addressed to talk, it retrieves data from the serial input buffer and outputs it to
the IEEE 488 bus. It substitutes the selected IEEE bus terminators for the received serial terminators. The
488 Controller will continue to output serial input-buffer data as long as the IEEE controller allows.
7.6.2 M
Y
L
ISTEN
A
DDRESS
(MLA)
When the 488 Controller is addressed to listen, it accepts data from the active talker and outputs this data
through the serial interface. It substitutes the selected serial terminators for the received IEEE bus
terminators.
CHAPTER 7: Peripheral Pass-Thru Operation
