3.4 Digital-I/O Section
3.4.1 TTL-Inputs
The standard models of the ME-630 series provide 8 TTL-inputs
(port A). Make sure that the signals are within the TTL-signal-level-
specifications (Low: 0 V…+0,8 V; High: +2,0 V…+5,5 V) and that
a connection to PC ground (Pin 1) exists.