b1 b2 b3 b4 b5 b6 b7 b8
1 character in the startstop system
Start bit Information bits
(8 bits including a parity bit)
Stop bits
(2 bits)
(For bit correspondence information, see the description of the SD and
RD signals in ltem 2).
The following codes are used:
i) EIA code + control codes DC1 to DC4
ii) ISO code + control codes DC1 to DC4
An I/O device must be able to identify the following control codes
output from the NC system:
Character 8 7 6 5 4 3 2 1
DC1 Start tape reader Ę ° Ę
DC2 Specify tape punch Ę ° Ę
DC3 Stop tape reader Ę Ę ° Ę Ę
DC4 Release tape punch Ę ° Ę
The control codes above are commonly used regardless of
whether the EIA code or ISO code is used.
With this interface, control codes DC1 to DC4 are used. Note the
(a) The NC machine can control an I/O device by sending DC1 to
(b)An I/O device can perform the operations below if it is not ready
to receive data from the NC machine.
(i) The I/O device can temporarily stop data transmission from
the NC machine by using the CS signal on the NC.
The CS signal, when turned off and sent to the NC machine,
causes the NC machine to stop data transmission after
sending a maximum of two characters including characters
currently being transmitted. When the CS signal is turned
on again, data transmission resumes.
(ii)When control code DC3 is sent to the NC machine, the NC
machine stops data transmission after sending 10 or less
characters. Then, when control code DC1 is sent to the NC
machine, the NC machine resumes data transmission. When
an I/O device containing an ISO/EIA converter is used, the
device needs to satisfy the specifications of Table 10.1.1.

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