參數(shù)資料
型號(hào): ST72324BLK4BA/XXX
廠商: STMICROELECTRONICS
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 8 MHz, MICROCONTROLLER, PDIP32
封裝: 0.400 INCH, PLASTIC, SDIP-32
文件頁數(shù): 56/151頁
文件大?。?/td> 1209K
代理商: ST72324BLK4BA/XXX
ST72F324L, ST72324BL
149/151
15.1.6 SCI Wrong Break duration
Description
A single break character is sent by setting and re-
setting the SBK bit in the SCICR2 register. In
some cases, the break character may have a long-
er duration than expected:
- 20 bits instead of 10 bits if M=0
- 22 bits instead of 11 bits if M=1.
In the same way, as long as the SBK bit is set,
break characters are sent to the TDO pin. This
may lead to generate one break more than expect-
ed.
Occurrence
The occurrence of the problem is random and pro-
portional to the baudrate. With a transmit frequen-
cy
of
19200
baud
(fCPU=8MHz
and
SCI-
BRR=0xC9), the wrong break duration occurrence
is around 1%.
Workaround
If this wrong duration is not compliant with the
communication protocol in the application, soft-
ware can request that an Idle line be generated
before the break character. In this case, the break
duration is always correct assuming the applica-
tion is not doing anything between the idle and the
break. This can be ensured by temporarily disa-
bling interrupts.
The exact sequence is:
- Disable interrupts
- Reset and Set TE (IDLE request)
- Set and Reset SBK (Break Request)
- Re-enable interrupts
15.2 ROM DEVICES ONLY
15.2.1 I/O Port A and F 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 A and F.
This happens with either one of the following con-
figurations:
PA3=0, PF4=1, PF1=0 when the PLL option is dis-
abled and PF0 is toggling
PA3=0, PF4=1, PF1=0, PF0=1 when the PLL op-
tion is enabled
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 (PF4 or PF0) or
VDD (PA3 or PF1).
15.3 FLASH DEVICES ONLY
15.3.1 Timer A Restrictions in Flash Devices
In Flash devices, Timer A functionality has the fol-
lowing restrictions:
– TAOC2HR and TAOC2LR registers are write
only
– Input Capture 2 is not implemented
– The corresponding interrupts cannot be used
(ICF2, OCF2 forced by hardware to zero)
15.3.2 External clock source with PLL
External clock source is not supported with the
PLL enabled.
15.3.3 39-Pulse ICC Entry Mode
ICC mode entry using ST7 application clock (39
pulses) is not supported. External clock mode
must be used (36 pulses). Refer to the ST7 Flash
Programming Reference Manual.
PLL PA3 PF4 PF1 PF0 Clock Disturbance
OFF
0
1
0
Tog-
gling
Max. 2 clock cycles
lost at each rising or
falling edge of PF0
ON
0
1
0
1
Max. 1 clock cycle
lost out of every 16
1
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