Mode 7 Overview
PSI BOX Reference
66-68 000-255
READ command returned data field.
70-72 000-255
RESET byte, The PSI BOX does Power On Reset when it
receives this byte.
74-76 000-255
Reserved.
78-80 000-255
EOS byte. PSI BOX recognises that this is the last
byte in a string sent by a talker. 000 when unused.
82
7 or 8
Number of bits to match in EOS byte. 7 or 8 bits.
84-86 000-255
END byte. PSI BOX only sends EOI true when this byte
is sent as last in a stream. When EOS width = 7 or 8
88
0,7 or 8
Number of bits to match in END byte. 7 or 8 bit
bytes. If =0 then never send EOI true when PSI BOX
sending data!
89
Comma
90
Carriage Return, End marker.
91-255
Reserved for future use. Make sure you allow for
these extra bytes.
The RESET Command and Character.
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Of particular interest is the RESET command and
character. Whenever the PSI BOX receives the reset character
from the RS232 host computer it performs a power on reset.
Everything is returned to the default state and an IEEE bus
ABORT command is performed. An ABORT command pulses
the IFC line for at least 100 micro seconds, then asserts the
REN and ATN lines true.
This reset function is to get you out of trouble if the IEEE
bus devices hang when , say, timeouts are disabled and a device
crashes. The default reset character is @ the Ascii character
decimal 64.
The RESET command can be used to specify which Ascii
character is to be used instead of the default character @, so
allowing for flexible data formats.
The Current Device.
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A concept that effects many bus operations is the current
device. The current device is extremely important since all data
sent via the PSI BOX in data pass through and all data received
from bus via the ENTER command is to and from the current
IEEE device. In addition, many of the IEEE controls and
Chapter 7
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