STA2416 datasheet(21/38 Pages) STMICROELECTRONICS

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STA2416

General specification

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General specification

6.1

System clock

The STA2416 works with a single clock provided on the XIN pin. The value of this external

clock should be any integer value from 12 … 33 MHz ±20 ppm (overall).

6.1.1

Slow clock

The slow clock is used by the baseband as reference clock during the low power modes.

The slow clock requires an accuracy of ±250 ppm (overall).

Several options are foreseen in order to adjust the STA2416 behavior according to the

features of the radio used.

●

If the system clock (for example, 13 MHz) is not provided at all times (power

consumption saving) and no slow clock is provided by the system, a 32 kHz crystal

must be used by the STA2416 (default mode).

●

If the system clock (for example, 13 MHz) is not provided at all times (power

consumption saving) and the system provides a slow clock at 32 kHz or 3.2 kHz, this

signal is simply connected to the STA2416 (LPO_CLK_P).

●

If the system clock (for example, 13 MHz) is provided at all times, the STA2416

generates from the reference clock an internal 32 kHz clock. This mode is not an

optimized mode for power consumption.

6.2

Boot procedure

The boot code instructions are the first that ARM7TDMI executes after a HW reset. All the

internal device's registers are set to their default value.

There are two types of boot:

●

Flash boot

When boot pin is set to ‘1’ (connected to VDD), the STA2416 boots on its flash

●

UART download boot from ROM

When boot pin is set to ‘0’ (connected to GND), the STA2416 boots on its internal ROM

(needed to download the new firmware in the flash). When booting on the internal

ROM, the STA2416 will monitor the UART interface for approximately 1.4 second. If

there is no request for code downloading during this period, the ROM jumps to flash.

6.3

Clock detection

The STA2416 has an automatic slow clock frequency detection (32kHz, 3.2kHz or none).

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