GW Instek GLA-1000 Series Quick start guide - Manual (Page 8)

Start Switch Triggers signal capturing. This is the
same functionality as the Single Run.
button.
Input Connector
For
Extension
Module
A0~D7 Signal input terminal. C0 ~ C7, D0 ~
D7 are not applicable to GLA-1016.
VDD, IOA/B/C,
GND +3.3V power, IO port, GND terminal
for extension module.
R_O, T_O, S_O Output signals for monitoring data
capturing and trigger timing. Read
output (R_O) indicates waveform
data is transferred to PC, Trigger
output (T_O) indicates trigger
condition has occurred, and Start
output (S_O) indicates GLA started
waiting for trigger condition.
CLK External (synchronous) clock signal
input, 0.001Hz ~ 100MHz.
GND Ground terminals.