
B–63083EN/02
5. CONNECTION TO CNC PERIPHERALS
67
Generally, two transmission methods are available at the serial interface.
Series 21i/210i use the start–stop method. With this method, start and stop
signals are output before and after each data bit.
One character in start–stop
b1 b2 b3 b4 b5 b6 b7 b8
Start
bit
Data bit
(8 bit including one parity bit)
Stop bits
(2 bits)
Transmission codes are as follows:
(i) EIA code and Control codes DC1 to DC4.
(ii)ISO code and Control codes DC1 to DC4 (Optional ISO code input is
necessary.)
The connected external device must be able to recognize the following
control codes, sent from NC.
Control code 8 7 6 5 4 3 2 1
DC1 Tape reader start f f f
DC2 Tape punch designation f f f
DC3 Tape reader stop f f f f
DC4 Tape punch release f f f f
NOTE
The listed control codes are used for both EIA and ISO.
In this interface, control codes DC1 to DC4 are used.
(a) NC can control external device by issuing codes DC1 to DC4.
(b)When external processing falls behind the pace of the NC signals
(When NC issues data)
(i) External device can temporarily stop NC data output by using the
NC’s CS signal. Data output stops within two characters including
a currently transmitting character when CS OFF signal is input to
NC. When CS signal is turned on again, data transmission start.
(ii)If control code DC3 is input to NC, NC stops data output within ten
characters. When control code DC1 is input to NC, NC starts
sending data again.
(c) When the external device is equipped with an ISO/EIA converter, the
external device must satisfy the specification shown in Table 5.2.4 (a).
Transmission Method of
RS–232C interface
Start–stop
Codes