ST72521AR9 STMicroelectronics, ST72521AR9 Datasheet - Page 212

• Manufacturer Part Number: ST72521AR9
• Description: 8-BIT MCU WITH NESTED INTERRUPTS, FLASH, 10-BIT ADC, FIVE TIMERS, SPI, SCI, I2C, CAN INTERFACE
• Manufacturer: STMicroelectronics

Specifications of ST72521AR9

• Hdflash Endurance: 100 cycles, data retention
• Clock Sources: crystal/ceramic resonator oscillators, internal RC oscillator and bypass for external clock
• Four Power Saving Modes: Halt, Active-Halt, Wait and Slow
• Main Clock Controller With: Real time base, Beep and Clock-out capabilities
• Two 16-bit Timers With: 2 input captures, 2 output compares, external clock input on one timer, PWM and pulse generator modes
• 8-bit Pwm Auto-reload Timer With: 2 input captures, 4 PWM outputs, output compare and time base interrupt, external clock with event detector

ST72F521, ST72521B
KNOWN LIMITATIONS (Cont’d)
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 (f
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
212/215
CPU
=8MHz and SCI-
15.1.7 16-bit Timer PWM Mode
In PWM mode, the first PWM pulse is missed after
writing the value FFFCh in the OC1R register
(OC1HR, OC1LR). It leads to either full or no PWM
during a period, depending on the OLVL1 and
OLVL2 settings.
15.1.8 CAN Cell Limitations
x=limitation present
1
2
WKPS bit.
3
Transmission workaround in Flash.
4
Not present in Flash and ROM Rev Y.
15.1.9 I2C Multimaster
In multimaster configurations, if the ST7 I2C re-
ceives a START condition from another I2C mas-
ter after the START bit is set in the I2CCR register
and before the START condition is generated by
the ST7 I2C, it may ignore the START condition
from the other I2C master. In this case, the ST7
master will receive a NACK from the other device.
On reception of the NACK, ST7 can send a re-start
and Slave address to re-initiate communication
Limitation
Omitted SOF bit
CPU write access
(more than one cycle)
corrupts CAN frame
Unexpected Mes-
sage transmission
Bus Off State Not En-
tered
WKPS Functionality
For details see
Software workaround possible using modified
Functionality modified for Unexpected Message
Limitation present on ROM Rev W and Rev Z.
1
section 10.8.5 on page 146
Flash
x
x
x
2
ROM
x
x
x
x
4
3