4-1SectionMovement of Data Carrier and Command Status
27
Polling Function
When an ordinary auto command is executed, the ID Controller does not re-
spond to the host computer until the Data Carrier approaches. Only when the
Data Carrier approaches, the communication line between the host computer
and the ID Controller becomes busy. However, when a polling auto command is
executed, the ID Controller returns a response to the host computer on request.
Therefore, the communication line ceases to be busy.
(Host computer) (ID Controller) (Data Carrier)
Subcommand
(Head)
(Inquiry to Head)
Subcommand
(Inquiry to Head 1)
Response
(Head)
Response
(Head not approaching)
(Head)
Response
(Head 1 processing end)
Not approaching
Not approaching
(Data Carrier)
Passing
Polling auto
command
Read/Write
processing
1, 2, 3... 1. The host computer sends a polling auto command to Head 1.
2. As soon as the ID Controller has received the command, it responds to the
host computer to indicate the reception of the command.
3. The host computer can make an inquiry on the progress of the processing or
terminate the polling auto processing by using a subcommand.
4. If the Data Carrier does not approach, the ID Controller responds to that ef-
fect to the host computer in response to a subcommand making an inquiry.
5. When the Data Carrier passes by the R/W Head, read or write processing is
performed.
6. When processing has ended, the ID Controller responds to the host comput-
er to indicate the end of the processing in response to a subcommand mak-
ing an inquiry.
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