ST72321 datasheet(182/185 Pages) STMICROELECTRONICS

182 / 185 page

ST72321

182/185

15.4 FLASH REV “S” and ROM Rev “Y”

DEVICES ONLY

15.4.1 I/O Port D Configuration

When using an external quartz crystal or ceramic

resonator, the fOSC2 clock may be disturbed be-

cause the device goes into reserved mode control-

led by Port D.

This happens with either one of the following con-

figurations:

– PD[3:1]=010 while CSS and PLL options are

both disabled and PD4 is toggling

– PD[4:1]=1010 while CSS or PLL options are en-

abled

This is detailed in the following table:

As a consequence, for cycle-accurate operations,

these configurations are prohibited in either input

or output mode.

Workaround:

To avoid this occurring, it is recommended to con-

nect one of these pins to GND (PD2 or PD4) or

VDD (PD1 or PD3).

15.5 ALL ROM DEVICES

15.5.1 LVD Operation

Depending on the operating conditions, especially

the VDD ramp up speed and ambient temperature,

in some cases the LVD may not start. When this

occurs, the MCU may operate outside the guaran-

teed functional area (see datasheet Figure 76)

without being forced into reset state.

In this case, proper use of the watchdog may

make it possible to recover through a watchdog re-

set and allow normal operations to resume.

Consequently, the LVD function is not guaranteed

in the current silicon revision. For complete securi-

ty, an external reset circuit must be added.

15.5.2 AVD not supported

On some devices with a specific VDD ramp up

speed the AVD may not start. As a result it cannot

generate interrupts when VDD rises and falls.

15.5.3 Internal RC oscillator operation

Internal RC oscillator operation is not supported in

ROM devices.

CSS

PLL PD[3:1]

PD4

Clock

Disturbance

OFF

010

Tog-

gling

Max. 2 clock cy-

cles lost at each

rising or falling

edge of PD4

xON

010

Max. 1 clock cy-

cle lost out of

every 16

ST72321 数据表(PDF) 182 Page - STMicroelectronics

ST72321 数据表(HTML) 182 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载