ZSSC3224 datasheet(21/51 Pages) IDT

21 / 51 page

ZSSC3224 Datasheet

October 24, 2016

3.4.

Operational Modes

Figure 3.2 illustrates the ZSSC3224 power-up sequence and subsequent operation depending on the selected interface

communication mode (I

2C or SPI) as determined by interface-related first activities after power-up or reset. If the first

command after power-up is a valid I²C command, the interface will function as an I²C interface until the next power-on

reset (POR). If there is no valid I²C command, but an active signal at the SS pin is detected as the first valid activity, then

the interface will respond as an SPI slave. With either interface, after the voltage regulators are switched on, the

ZSSC3224

’s low-voltage section (LV) is active while the related interface configuration information is read from memory.

Then the LV section is switched off, the ZSSC3224 goes into Sleep Mode, and the interface is ready to receive

commands. The interface is always powered by VDD, so it is referred to as the high voltage section (HV).

See Table 3.1 for definitions of the commands.

Figure 3.3 shows the ZSSC3224 operation in Normal Mode

(with two operation principles: “Sleep” and “Cyclic”) and

Command Mode, including when the LV and HV sections are active as indicated by the color legend. The Normal Mode

automatically returns to Sleep Mode after executing the requested measurements, or periodically wakes up and conducts

another measurement according to the setting for the sleep duration configured by CYC_period (bits[14:12] in memory

which is helpful during calibration. Command Mode can only be entered if Start_CM (command A9HEX; see Table 3.1) is

the first command received after a POR.

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