ST10F272B_12 STMICROELECTRONICS [STMicroelectronics], ST10F272B_12 Datasheet - Page 162

• Manufacturer Part Number: ST10F272B_12
• Description: 16-bit MCU with 256 Kbyte Flash memory and 12/20 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Electrical characteristics
Table 76.
Note:
24.8.14
162/188
XTAL1 period
High time
Low time
Rise time
Fall time
Parameter
3
3
3
3
External clock drive
1. The minimum value for the XTAL1 signal period shall be considered as the theoretical minimum. The real
2. 4-8 MHz is the input frequency range when using an external clock source. 64 MHz can be applied with an
3. The input clock signal must reach the defined levels V
Figure 48. External clock drive XTAL1
When Direct Drive is selected, an external clock source can be used to drive XTAL1. The
maximum frequency of the external clock source depends on the duty cycle: when 64MHz is
used, 50% duty cycle shall be granted (low phase = high phase = 7.8ns); when for instance
32MHz is used, a 25% duty cycle can be accepted (minimum phase, high or low, again
equal to 7.8ns).
Memory cycle variables
The tables below use three variables which are derived from the BUSCONx registers and
represent the special characteristics of the programmed memory cycle.
how these variables are to be computed.
Table 77.
1, 2
ALE Extension
Memory Cycle Time wait states
Memory Tri-state Time
minimum value depends on the duty cycle of the input clock signal.
external clock source only when Direct Drive mode is selected: in this case, the oscillator amplifier is
bypassed so it does not limit the input frequency.
t
t
t
t
t
OSC
1
2
3
4
Symbol
SR
SR
SR
SR
SR
Description
Memory cycle variables
15.625
min.
Direct drive
f
6
6
–
–
CPU
= f
XTAL
max.
–
–
–
2
2
Doc ID 11917 Rev 3
Direct drive with
f
min.
83.3
Symbol
CPU
3
3
–
–
prescaler
t
t
t
C
A
F
= f
XTAL
IL2
max.
250
–
–
2
2
and V
/ 2
TCL x [ALECTL]
2TCL x (15 - [MCTC])
2TCL x (1 - [MTTC])
IH2
f
.
CPU
min.
83.3
PLL usage
6
6
–
–
= f
XTAL
max.
250
ST10F272B/ST10F272E
–
–
2
2
Values
x F
Table 77
Unit
ns
ns
ns
ns
ns
describes,