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| 型号： | MC68L11D0FNE2 |
| 厂商： | FREESCALE SEMICONDUCTOR INC |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 8-BIT, 2 MHz, MICROCONTROLLER, PQCC44 |
| 封装： | PLASTIC, LCC-44 |
| 文件页数： | 104/138页 |
| 文件大小： | 1047K |
| 代理商： | MC68L11D0FNE2 |
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Serial Communications Interface (SCI)
MC68HC711D3 Data Sheet, Rev. 2.1
68
Freescale Semiconductor
6.5 Wakeup Feature
The wakeup feature reduces SCI service overhead in multiple receiver systems. Software for each
receiver evaluates the first character of each message. The receiver is placed in wakeup mode by writing
a 1 to the RWU bit in the SCCR2 register. While RWU is 1, all of the receiver-related status flags (RDRF,
IDLE, OR, NF, and FE) are inhibited (cannot become set). Although RWU can be cleared by a software
write to SCCR2, to do so would be unusual. Normally, RWU is set by software and is cleared
automatically with hardware. Whenever a new message begins, logic alerts the sleeping receivers to
wake up and evaluate the initial character of the new message.
Two methods of wakeup are available:
Idle line wakeup
Address mark wakeup
During idle line wakeup, a sleeping receiver awakens as soon as the RxD line becomes idle. In the
address mark wakeup, logic 1 in the most significant bit (MSB) of a character wakes up all sleeping
receivers.
6.5.1 Idle-Line Wakeup
To use the receiver wakeup method, establish a software addressing scheme to allow the transmitting
devices to direct a message to individual receivers or to groups of receivers. This addressing scheme can
take any form as long as all transmitting and receiving devices are programmed to understand the same
scheme. Because the addressing information is usually the first frame(s) in a message, receivers that are
not part of the current task do not become burdened with the entire set of addressing frames. All receivers
are awake (RWU = 0) when each message begins. As soon as a receiver determines that the message
is not intended for it, software sets the RWU bit (RWU = 1), which inhibits further flag setting until the RxD
line goes idle at the end of the message. As soon as an idle line is detected by receiver logic, hardware
automatically clears the RWU bit so that the first frame of the next message can be received. This type
of receiver wakeup requires a minimum of one idle-line frame time between messages and no idle time
between frames in a message.
6.5.2 Address-Mark Wakeup
The serial characters in this type of wakeup consist of seven (eight if M = 1) information bits and an MSB,
which indicates an address character (when set to 1 — mark). The first character of each message is an
addressing character (MSB = 1). All receivers in the system evaluate this character to determine if the
remainder of the message is directed toward this particular receiver. As soon as a receiver determines
that a message is not intended for it, the receiver activates the RWU function by using a software write to
set the RWU bit. Because setting RWU inhibits receiver-related flags, there is no further software
overhead for the rest of this message. When the next message begins, its first character has its MSB set,
which automatically clears the RWU bit and enables normal character reception. The first character
whose MSB is set is also the first character to be received after wakeup because RWU gets cleared
before the stop bit for that frame is serially received. This type of wakeup allows messages to include gaps
of idle time, unlike the idle-line method, but there is a loss of efficiency because of the extra bit time for
each character (address bit) required for all characters.
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相关代理商/技术参数 |
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| MC68L11E0FN2 | 制造商:Rochester Electronics LLC 功能描述:8-BIT MCU,512RAM,A/D,LVDC - Bulk |
| MC68L11E0FNE2 | 功能描述:IC MCU 8BIT LV 512RAM 52-PLCC RoHS:是 类别:集成电路 (IC) >> 嵌入式 - 微控制器， 系列:HC11 标准包装:1 系列:87C 核心处理器:MCS 51 芯体尺寸:8-位 速度:16MHz 连通性:SIO 外围设备:- 输入/输出数:32 程序存储器容量:8KB（8K x 8） 程序存储器类型:OTP EEPROM 大小:- RAM 容量:256 x 8 电压 - 电源 (Vcc/Vdd):4 V ~ 6 V 数据转换器:- 振荡器型:外部 工作温度:0°C ~ 70°C 封装/外壳:44-DIP 包装:管件 其它名称:864285 |
| MC68L11E1CFNE2 | 功能描述:8位微控制器 -MCU 8B MCU RAM EE A/D LVDC 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 |
| MC68L11E1FNE2 | 功能描述:8位微控制器 -MCU 8B MCU RAM EE A/D LVD 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 |
| MC68L11F1CFNE3 | 功能描述:8位微控制器 -MCU 8B MCU 1KRAM 512BYTES 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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