67
The following timing charts show the transmission timing in half-duplex commu-
nications in which the host computer is sending data.
(2)
Command
Command
1
0
Command
Command
Response required
Host computer
Host Link Unit
Response
Response
Execution possible flag
Reception of command End of reception
Response not required
Host Link Unit
Execution possible flag
Reception of command
End of reception
Response
Host computer
(2)
(1)
(1)
1
0
A command from the Host Link Unit to the host computer is transmitted only after
the Host Link Unit completes receiving the command from the host computer
(refer to the above (1). A response of the Host Link Unit for a command from the
host computer will be transmitted only after the command to the host computer is
completed (if a response for the command is required, then the response of the
Host Link Unit will be transmitted only after the response is received by the Host
Link Unit) (refer to (2) of the above). If no response from the host computer is
required, the execution possible flag will turn ON when the command to the host
computer is delivered from the PC to the Host Link Unit.
The following timing charts show the transmission timing in half-duplex commu-
nications in which a command is sent while the host computer is receiving data.
Command
Command
1
0
Command
Command
Response required
Host computer
Host Link Unit
Response
Response
Execution possible flag
Reception of command
End of reception
Response not required
Host Link Unit
Execution possible flag
Reception of command
End of reception
Response
Host computer
(2)(1)
1
0
(1) (2)
The above timing charts show that the Host Link Unit is transmitting a response
for a command from the host computer (refer to (1)), in which case a command to
the host computer from the Host Link Unit will be transmitted only after the Host
Half-duplex
Communications
Communications Timing Section 4-5
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