Motorola MCU 68HC912D60 Bedienungsanleitung PDF herunterladen (Seite 11)

68HC912D60MSE4 Rev 2 11

March 14, 2001

Lastly, an alternative and simpler approach is to just hold reset low for a substantial

time (> 100 milliseconds) after Vdd has reached the operating voltage range.

In some applications it may be possible avoid this issue by delaying the connection

of Vddpll to Vdd until the device has exited reset. This will sacrifice the limp home

mode safety function upon startup, i.e. the part will no longer be able to start

without a functioning crystal. A similar technique (disable PLL under software

control) can be used to overcome the limitations of Stop mode.

Figure 1. Representation of Normal start-up condition

Power ON

13-bit WCR

counter

Ext Reset pin

Osc. Extal

LH mode

sysclock

4096

count

point

EXTAL derived clock

PLL clock

Limp-Home mode start-up issue

1 2 ... 6 7 8 9 10 11 12 13

Keine Kommentare

Motorola MCU 68HC912D60 Bedienungsanleitung Seite 11