Next Advance SP1800 - Manual (Page 49)

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SP1600/1800 Programmable Syringe Pump
Publication #1200-02 44 9/15/04
10. Logic Interface: TTL Input and Output
Figure 2: Rear of Pump
On the rear of the pump is a DB-9 connector, below the ‘TTL-I/O’ label, which is used for TTL I/O. The
logic signals on this connector permit bi-directional control with external equipment.
Control input TTL logic levels must be held steady for a minimum of 100 ms to be recognized. To
minimize the possibility of false signals caused by glitches and ringing, which could be caused by the
closure of mechanical switches, TTL control inputs are software filtered. With a sampling period of 50
ms, glitches of less then 100 ms are filtered out.
Edge detection requires the detection of a change in TTL levels. With a minimum of 100 ms to detect a
level, an edge requires a minimum of 200 ms to be detected. Since the next level change can be detected
in 100 ms, creating another edge, the maximum edge to edge frequency is 10 Hz.
Edge changes to the ‘Pumping Direction’ and ‘Operational Trigger’ inputs must occur at least 50 ms apart.
Falling edge refers to a logic high to logic low transition. Rising edge refers to a logic low to a logic high
transition. To guarantee recognition of logic levels, voltages on the input lines must be within the
following ranges:
TTL logic low (0): 0 to 1.5 V
logic high (1): 3.5 to 5.25 V
The Vcc and Ground pins, pins 1 and 9, are for logic reference only. To assure proper voltage levels, the
Ground pin should always be connected to the signal ground of a sensing or controlling device that is
attached to any other pin on the TTL I/O connector. The Vcc pin should not be used to source current.
The TTL I/O pins are defined as follows:
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