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| 型号： | AT89LP51-20PU |
| 厂商： | Atmel |
| 文件页数： | 86/117页 |
| 文件大小： | 0K |
| 描述： | MCU 8051 4K FLASH 20MHZ |
| 标准包装： | 10 |
| 系列： | 89LP |
| 核心处理器： | 8051 |
| 芯体尺寸： | 8-位 |
| 速度： | 20MHz |
| 连通性： | EBI/EMI，I²C，SPI，UART/USART |
| 外围设备： | 欠压检测/复位，POR，PWM，WDT |
| 输入/输出数： | 36 |
| 程序存储器容量： | 4KB（4K x 8） |
| 程序存储器类型： | 闪存 |
| RAM 容量： | 256 x 8 |
| 电压 - 电源 (Vcc/Vdd)： | 2.4 V ~ 5.5 V |
| 振荡器型： | 内部 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 40-DIP（0.600"，15.24mm） |
| 包装： | 管件 |
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70
3709D–MICRO–12/11
AT89LP51/52
14.7
More About Modes 2 and 3
Eleven bits are transmitted (through TXD), or received (through RXD): a start bit (0), 8 data bits
(LSB first), a programmable 9th data bit, and a stop bit (1). On transmit, the 9th data bit (TB8)
can be assigned the value of “0” or “1”. On receive, the 9th data bit goes into RB8 in SCON. The
baud rate is programmable to either 1/16 or 1/32 of the oscillator frequency in Mode 2. Mode 3
may have a variable baud rate generated from either Timer 1 or Timer 2, depending on the state
of RCLK and TCLK.
Figures 14-7 and 14-8 show a functional diagram of the serial port in Modes 2 and 3. The
receive portion is exactly the same as in Mode 1. The transmit portion differs from Mode 1 only
in the 9th bit of the transmit shift register.
Transmission is initiated by any instruction that uses SBUF as a destination register. The “write
to SBUF” signal also loads TB8 into the 9th bit position of the transmit shift register and flags the
TX Control unit that a transmission is requested. Transmission commences at S1P1 of the
machine cycle following the next rollover in the divide-by-16 counter. Thus, the bit times are syn-
chronized to the divide-by-16 counter, not to the “write to SBUF” signal.
The transmission begins when SEND is activated, which puts the start bit at TXD. One bit time
later, DATA is activated, which enables the output bit of the transmit shift register to TXD. The
first shift pulse occurs one bit time after that. The first shift clocks a “1” (the stop bit) into the 9th
bit position of the shift register. Thereafter, only “0”s are clocked in. Thus, as data bits shift out to
the right, “0”s are clocked in from the left. When TB8 is at the output position of the shift register,
then the stop bit is just to the left of TB8, and all positions to the left of that contain “0”s. This con-
dition flags the TX Control unit to do one last shift, then deactivate SEND and set TI. This occurs
at the 11th divide-by-16 rollover after “write to SBUF.”
Reception is initiated by a 1-to-0 transition detected at RXD. For this purpose, RXD is sampled
at a rate of 16 times the established baud rate. When a transition is detected, the divide-by-16
counter is immediately reset, and 1FFH is written to the input shift register.
At the 7th, 8th and 9th counter states of each bit time, the bit detector samples the value of RXD.
The value accepted is the value that was seen in at least 2 of the 3 samples. If the value
accepted during the first bit time is not 0, the receive circuits are reset and the unit continues
looking for another 1-to-0 transition. If the start bit proves valid, it is shifted into the input shift
register, and reception of the rest of the frame proceeds.
As data bits come in from the right, “1”s shift out to the left. When the start bit arrives at the left-
most position in the shift register (which in Modes 2 and 3 is a 9-bit register), it flags the RX Con-
trol block to do one last shift, load SBUF and RB8, and set RI. The signal to load SBUF and RB8
and to set RI is generated if, and only if, the following conditions are met at the time the final shift
pulse is generated:
RI = 0, and
Either SM2 = 0 or the received 9th data bit = 1
If either of these conditions is not met, the received frame is irretrievably lost, and RI is not set. If
both conditions are met, the received 9th data bit goes into RB8, and the first 8 data bits go into
SBUF. One bit time later, whether the above conditions were met or not, the unit continues look-
ing for a 1-to-0 transition at the RXD input.
Note that the value of the received stop bit is irrelevant to SBUF, RB8, or RI.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AT89LP51ED2-20AAU | 功能描述:8位微控制器 -MCU 64KB 20MHz 2.4V-5.5V 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 |
| AT89LP51ED2-20AU | 功能描述:8位微控制器 -MCU 64KB 20MHz 2.4V-5.5V 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 |
| AT89LP51ED2-20JU | 功能描述:8位微控制器 -MCU 64KB 20MHz 2.4V-5.5V 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 |
| AT89LP51ED2-20MU | 功能描述:8位微控制器 -MCU 64KB 20MHz 2.4V-5.5V 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 |
| AT89LP51ED2-20PU | 功能描述:8位微控制器 -MCU 64KB 20MHz 2.4V-5.5V 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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