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型号： ATMEGA6490V-8AI
厂商： Atmel
文件页数： 22/146页
文件大小： 0K
描述： IC AVR MCU FLASH 64K 1.8 100TQFP
产品培训模块： megaAVR Introduction
标准包装： 90
系列： AVR® ATmega
核心处理器： AVR
芯体尺寸： 8-位
速度： 8MHz
连通性： SPI，UART/USART，USI
外围设备： 欠压检测/复位，LCD，POR，PWM，WDT
输入/输出数： 68
程序存储器容量： 64KB（32K x 16）
程序存储器类型： 闪存
EEPROM 大小： 2K x 8
RAM 容量： 4K x 8
电压 - 电源 (Vcc/Vdd)： 1.8 V ~ 5.5 V
数据转换器： A/D 8x10b
振荡器型： 内部
工作温度： -40°C ~ 85°C
封装/外壳： 100-TQFP
包装： 托盘
配用： ATSTK600-TQFP100-ND - STK600 SOCKET/ADAPTER 100-TQFP
ATSTK504-ND - STARTER KIT AVR EXP MOD 100P LCD
PIC16(L)F1825/1829
DS41440C-page 270
2010-2012 Microchip Technology Inc.
25.5.5
CLOCK STRETCHING
Clock stretching occurs when a device on the bus
holds the SCLx line low effectively pausing communi-
cation. The slave may stretch the clock to allow more
time to handle data or prepare a response for the
master device. A master device is not concerned with
stretching as anytime it is active on the bus and not
transferring data it is stretching. Any stretching done
by a slave is invisible to the master software and
handled by the hardware that generates SCLx.
The CKP bit of the SSPxCON1 register is used to con-
trol stretching in software. Any time the CKP bit is
cleared, the module will wait for the SCLx line to go
low and then hold it. Setting CKP will release SCLx
and allow more communication.
25.5.5.1
Normal Clock Stretching
Following an ACK if the R/W bit of SSPxSTAT is set, a
read request, the slave hardware will clear CKP. This
allows the slave time to update SSPxBUF with data to
transfer to the master. If the SEN bit of SSPxCON2 is
set, the slave hardware will always stretch the clock
after the ACK sequence. Once the slave is ready; CKP
is set by software and communication resumes.
25.5.5.2
10-bit Addressing Mode
In 10-bit Addressing mode, when the UA bit is set, the
clock is always stretched. This is the only time the
SCLx is stretched without CKP being cleared. SCLx is
released immediately after a write to SSPxADD.
25.5.5.3
Byte NACKing
When AHEN bit of SSPxCON3 is set; CKP is cleared
by hardware after the 8th falling edge of SCLx for a
received matching address byte. When DHEN bit of
SSPxCON3 is set; CKP is cleared after the 8th falling
edge of SCLx for received data.
Stretching after the 8th falling edge of SCLx allows the
slave to look at the received address or data and
decide if it wants to ACK the received data.
25.5.6
CLOCK SYNCHRONIZATION AND
THE CKP BIT
Any time the CKP bit is cleared, the module will wait
for the SCLx line to go low and then hold it. However,
clearing the CKP bit will not assert the SCLx output
low until the SCLx output is already sampled low.
Therefore, the CKP bit will not assert the SCLx line
until an external I2C master device has already
asserted the SCLx line. The SCLx output will remain
low until the CKP bit is set and all other devices on the
I2C bus have released SCLx. This ensures that a write
to the CKP bit will not violate the minimum high time
requirement for SCLx (see Figure 25-23).
FIGURE 25-23:
CLOCK SYNCHRONIZATION TIMING
Note 1:
The BF bit has no effect on if the clock will
be stretched or not. This is different than
previous versions of the module that
would not stretch the clock, clear CKP, if
SSPxBUF was read before the 9th falling
edge of SCLx.
2:
Previous versions of the module did not
stretch the clock for a transmission if
SSPxBUF was loaded before the 9th
falling edge of SCLx. It is now always
cleared for read requests.
Note:
Previous versions of the module did not
stretch the clock if the second address byte
did not match.
SDAx
SCLx
DX
– 1
DX
WR
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
SSPxCON1
CKP
Master device
releases clock
Master device
asserts clock
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ATmega6490V-8AU 功能描述:8位微控制器 -MCU AVR 64K FLASH 2K EE 4K SRAM ADC LCD 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
ATMEGA6490V-8AUR 功能描述:8位微控制器 -MCU AVR 64KB FLSH 2KB EE 4KB SRAM LCD8MHz1.8V 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
ATmega649-16AI 功能描述:8位微控制器 -MCU AVR 64K FLASH 2K EE 4K SRAM ADC LCD 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
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ATMEGA649-16AUR 功能描述:8位微控制器 -MCU AVR 64KB FLSH 2KB EE 4KB SRAM LCD16MHz,5V 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
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