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参数资料
型号： ST72T121J2B6
厂商： STMICROELECTRONICS
元件分类： 微控制器/微处理器
英文描述： 8-BIT, OTPROM, 8 MHz, MICROCONTROLLER, PDIP42
封装： 0.600 INCH, SHRINK, PLASTIC, DIP-42
文件页数： 64/93页
文件大小： 597K
代理商： ST72T121J2B6
67/93
ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.4.3 Data Transfer Format
During an SPI transfer, data is simultaneously
transmitted (shifted out serially) and received
(shifted in serially). The serial clock is used to syn-
chronize the data transfer during a sequence of
eight clock pulses.
The SS pin allows individual selection of a slave
device; the other slave devices that are not select-
ed do not interfere with the SPI transfer.
Clock Phase and Clock Polarity
Four possible timing relationships may be chosen
by software, using the CPOL and CPHA bits.
The CPOL (clock polarity) bit controls the steady
state value of the clock when no data is being
transferred. This bit affects both master and slave
modes.
The combination between the CPOL and CPHA
(clock phase) bits selects the data capture clock
edge.
Figure 38, shows an SPI transfer with the four
combinations of the CPHA and CPOL bits. The di-
agram may be interpreted as a master or slave
timing diagram where the SCK pin, the MISO pin,
the MOSI pin are directly connected between the
master and the slave device.
The SS pin is the slave device select input and can
be driven by the master device.
The master device applies data to its MOSI pin-
clock edge before the capture clock edge.
CPHA bit is set
The second edge on the SCK pin (falling edge if
the CPOL bit is reset, rising edge if the CPOL bit is
set) is the MSBit capture strobe. Data is latched on
the occurrence of the second clock transition.
No write collision should occur even if the SS pin
stays low during a transfer of several bytes (see
Figure 37).
CPHA bit is reset
The first edge on the SCK pin (falling edge if CPOL
bit is set, rising edge if CPOL bit is reset) is the
MSBit capture strobe. Data is latched on the oc-
currence of the first clock transition.
The SS pin must be toggled high and low between
each byte transmitted (see Figure 37).
To protect the transmission from a write collision a
low value on the SS pin of a slave device freezes
the data in its DR register and does not allow it to
be altered. Therefore the SS pin must be high to
write a new data byte in the DR without producing
a write collision.
Figure 37. CPHA / SS Timing Diagram
MOSI/ MISO
Master
SS
Slave
SS
(CPHA=0)
Slave
SS
(CPHA=1)
Byte 1
Byte 2
Byte 3
VR02131A
67
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相关代理商/技术参数
参数描述
ST72T121J2T6 功能描述:8位微控制器 -MCU OTP EPROM 8K SPI/SCI RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
ST72T121J2T6S 制造商:STMicroelectronics 功能描述:
ST72T121J4B6 功能描述:8位微控制器 -MCU OTP EPROM 16K SPI/SC RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
ST72T121J4T6 功能描述:8位微控制器 -MCU OTP EPROM 16K SPI/SC RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
ST72T121J4T6S 制造商:STMicroelectronics 功能描述:
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