ZSC31014 datasheet(28/58 Pages) IDT

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ZSC31014 Datasheet

January 20, 2016

3.1.1. Update Mode

In Update Mode, the digital core will perform measurements and correction calculations at a selectable update

rate and update the I

2C™/SPI output register. The power-on measurement sequence for the Update Mode is

shown in Figure 3.2.

Figure 3.2

Power-Up Sequence and Timing for Update Mode with EEPROM Locked

If the part is programmed for the fastest update rate, conversions will continue to happen after the power-up

sequence. If the ZSC31014 is not in the fastest update rate, the part will power down after writing to the digital

output register. The duration of the power-down period is determined by the Update_Rate setting (bits [7:6] in

EEPROM word 01HEX; see section 3.6) and the digital core clock speed (see section 2.3.6). See Table 3.2 and

Table 3.3 for the update rates. After the power-down period has expired, the ZSC31014 will power up; take

another bridge reading followed by calculations; write to the digital output register; and power down. Temperature

and Auto-Zero (AZ) are slower moving quantities but must be updated periodically. When the part is configured in

Update Mode, these two quantities are measured periodically (referred to as special measurements).

As illustrated in Figure 3.3, valid data output to the digital register occurs after the measurement and the DSP

calculations are complete. At this point the master can fetch the data in I

2C™ or SPI with a Read_DF command.

Specifics of the Read_DF command are given in sections 3.2 and 3.3. After a valid output has been read by the

master, the status bits are set to “stale,” indicating that the measurement has not been updated since the last

Read_DF. This mode allows the application to simply read the digital output at any time and be assured the data

is no older than the selected update period. See Table 2.9 for more information on the status bits. The chip should

be polled at a frequency slower than 20% more of the update rate period listed in Table 3.2 and Table 3.3.

In I

2C™ Mode only, the INT/SS pin will assume the INT (interrupt) function. Instead of polling until a “valid”

response is received, the application can look for a rise on the INT pin. This will indicate that the measurement

and calculations are complete and new valid data is ready to be read on the I

2C™ interface.

When EEPROM is not locked, the command window is 4.5ms longer (= 6ms). All time values shown are typical; for the worst case values,

multiply by 1.15 (nominal frequency ±15%).

Command

Window

Temperature

Measurement

AutoZero (AZ)

Measurement

Bridge

Measurement

1.5ms

1.4ms

400

µs

Power applied to device.

Command window starts after

a short power-on-reset window.

DSP

Calculations

st corrected signal measurement

written to digital output register

2C™ or SPI)

1.4ms

400

µs

1.4ms

400

µs

220

µs

With 1MHz CLK

execution time

With 4MHz CLK

execution time

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