Control Functions
PSI BOX PLUS+ Reference
TAD.
Sends The Talk Address.
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Purpose.
The talk address is sent to the IEEE bus.
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The TAD command is used to send one talk address in the
range 0 to 30 to the bus devices.
The PSI BOX asserts ATN and becomes the active
controller, then the number entered by the user is ORed with hex
040h, 64 decimal, and is sent over the IEEE bus. After the
command has been sent the ATN remains true, PSI BOX is the
active controller.
The TAD is used to instruct one bus device that it is the
active talker following in the Serial Poll routine or in data
transfers. Only one talker can be active, addressed at one time
else confusion would reign! The TAD command is treated as an
UNTALK command by all the other talkers. When the current
talker recognises that another talker has been addressed to talk
then it is automatically put in the untalk state. The TAD
command can also be sent by using CMD 64-94 or CMD 192-
222 or by using TALK 0-30 or 128-158
Format.
TAD 1
Tell device 1 to talk.
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TAD 1+2
Device 1 with Secondary address 2,
is the new talker.
Params.
One parameter only in the range 0-30 or 128 - 158.
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An optional secondary address can be specified for
the primary address by using +sa after the primary
address. The sa is also in the range 0-30.
Returns.
None.
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Example.
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_
BUS TAD 1+2 ;tell device 1 with second address 2 to talk.
Bus Activity.
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_
assert ATN if not already so
TAD 1
SCG 2
Chapter 8
Page 151
