MKS 651D Series, User Manual, Page: 127 / 162

Chapter Six: Remote Digital Logic Control How To Select the Digital Output Functions
115
How To Select the Digital Output Functions
The I/O board contains 6 type 74HC digital outputs , each having the capacity to drive one
standard TTL load. The specific function of each output is listed in Table 19, page 116. The
approximate time constant of the outputs are 2.5 microseconds. Each output includes a 240
ohms series resistor to protect it against line surges and spikes. Additionally, there is a 0.01 µFD
capacitor connected to the chassis.
µFD
From output port
(74HC377)
R
240 ohms
I/O Connector
0.01
µFD 0.01
Digital Ground
= Internal resistance
of output driver
25 ohms sinking/
50 ohms sourcing)
int
R
int
Figure 17: I/O Board Digital Output Circuitry