PS081 datasheet(34/155 Pages) AMSCO

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3-11

PSØ81

Cycle Time

fixed

The discharge time is given by the value of the strain gage resistor and the given capacitor Cload.

The recommended discharge time is in the range of 80 to 150 µs (at 3.3V). The charge time has to

be long enough to provide a full recharge of Cload and is typically 30% of the cycle time. If the cycle

time is set too small (in the range of the discharge time or smaller) an overflow will occur.

The cycle time is set in register 2, cytime[13:4]. The cycle time is normally generated by the high

speed clock and can be set in steps of 2 µs. The only exception is the “Stretched Mode” (see chapter

‚Modes‘ 3.5) where the cycle time is generated by the internal 10 kHz oscillator and therefore confi-

gurable in steps of 100 µs.

Example:

cytime[13:4] = 80

80 x 2 µs = 160 µs cycle time in all modes except stretched mode

cytime[13:4] = 10

10 x 100 µs = 1 ms cycle time in stretched mode

The recommended minimum cycle time setting is 1.4 times the discharge time. E.g. 140 µs if the

discharge time is 100 µs.

3.4.3

Cycle Time in Stretched Mode

In stretched mode the parameter cyctime has a special function. In this case, it does NOT define the

time of discharging + charging, instead it defines the time between 2 discharging cycles in multiples

of 100 µs:

Figure 3.13: Cycle time in streched mode

There are several parameters to adjust in stretched mode. Please have a look at Stretched Mode

settings in section 3.5.3.

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