Parallax P2 Edge Module - Datasheet

Dual Boot Memory

Dual Boot Memory Connections

● Refer to all requirements and recommendations for Minimal Connections

● The Boot Mode Selection switch determines the active boot device; either SPI Flash or microSD.

● Switch closed (on) = SPI Flash boot mode : When the Propeller 2 starts up (or is reset) with this circuit,

there will be a serial programming window of 100 ms, then automatic boot from ﬁrmware stored in the

SPI ﬂash memory. If SPI ﬂash boot fails, a further serial window of 60 seconds will be followed by

shutdown.

● Switch open (off) = microSD boot mode : When the Propeller 2 starts up (or is reset) with this circuit, it will

automatically boot from ﬁrmware saved on the microSD card. If microSD boot fails then a further serial

window of 60 seconds will be followed by shutdown.

OPERATION

Assuming a stable power supply and "high" RESn pin, the Propeller 2 boots up using the following procedure

procedure:

1. Within 5 ms, the Propeller 2 loads its Bootloader into cog 0.

2. The Bootloader checks the Boot Pattern (conﬁguration) on pins P59-P61 and either receives a new

Propeller Application over serial, or loads (boots) the application from a connected ﬂash chip or SD card.

3. All further activity is deﬁned by the application itself. The application, and thus the developer, has

complete control over modifying internal clock speed, I/O pin usage and behavior, what cogs are running

at any given time, and more.

4. The Propeller continues running until all cogs shut each other (or themselves) down, the RESn pin goes

low, or the application requests a reboot.