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参数资料
| 型号： | ST72141K2B3/XXX |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 8-BIT, MROM, 8 MHz, MICROCONTROLLER, PDIP32 |
| 封装： | 0.400 INCH, PLASTIC, SDIP-32 |
| 文件页数： | 5/133页 |
| 文件大小： | 2615K |
| 代理商： | ST72141K2B3/XXX |
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Obsolete
Product(s)
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ST72141K2
102/133
SERIAL PERIPHERAL INTERFACE (Cont’d)
8.4.4.4 Write Collision Error
A write collision occurs when the software tries to
write to the DR register while a data transfer is tak-
ing place with an external device. When this hap-
pens, the transfer continues uninterrupted; and
the software write will be unsuccessful.
Write collisions can occur both in master and slave
mode.
Note: a "read collision" will never occur since the
received data byte is placed in a buffer in which
access is always synchronous with the MCU oper-
ation.
In Slave mode
When the CPHA bit is set:
The slave device will receive a clock (SCK) edge
prior to the latch of the first data transfer. This first
clock edge will freeze the data in the slave device
DR register and output the MSBit on to the exter-
nal MISO pin of the slave device.
The SS pin low state enables the slave device but
the output of the MSBit onto the MISO pin does
not take place until the first data transfer clock
edge.
When the CPHA bit is reset:
Data is latched on the occurrence of the first clock
transition. The slave device does not have any
way of knowing when that transition will occur;
therefore, the slave device collision occurs when
software attempts to write the DR register after its
SS pin has been pulled low.
For this reason, the SS pin must be high, between
each data byte transfer, to allow the CPU to write
in the DR register without generating a write colli-
sion.
In Master mode
Collision in the master device is defined as a write
of the DR register while the internal serial clock
(SCK) is in the process of transfer.
The SS pin signal must be always high on the
master device.
WCOL bit
The WCOL bit in the SR register is set if a write
collision occurs.
No SPI interrupt is generated when the WCOL bit
is set (the WCOL bit is a status flag only).
Clearing the WCOL bit is done through a software
sequence (see Figure 60).
Figure 60. Clearing the WCOL bit (Write Collision Flag) Software Sequence
Clearing sequence after SPIF = 1 (end of a data byte transfer)
1st Step
Read SR
Read DR
Write DR
2nd Step
SPIF =0
WCOL=0
SPIF =0
WCOL=0 if no transfer has started
WCOL=1 if a transfer has started
Clearing sequence before SPIF = 1 (during a data byte transfer)
1st Step
2nd Step
WCOL=0
before the 2nd step
Read SR
Read DR
Note: Writing to the DR register
instead of reading in it does not
reset the WCOL bit
Read SR
OR
THEN
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相关代理商/技术参数 |
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|---|---|
| ST72141K2B6 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH ELECTRIC-MOTOR CONTROL, ADC, 16-BIT TIMERS, SPI INTERFACE |
| ST72141K2M1 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH ELECTRIC-MOTOR CONTROL, ADC, 16-BIT TIMERS, SPI INTERFACE |
| ST72141K2M3 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH ELECTRIC-MOTOR CONTROL, ADC, 16-BIT TIMERS, SPI INTERFACE |
| ST72141K2M3/XXX | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Microcontroller |
| ST72141K2M6 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH ELECTRIC-MOTOR CONTROL, ADC, 16-BIT TIMERS, SPI INTERFACE |
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