3BHE005555R0101工业自动化卡件
FSK输入（现场总线模式）仅适用于现场总线模式下的LDSYN-101工业自动化卡件，所有数据和通信均为共享总线上的FSK编码数字信号，需要解码。微处理器可以通过指定设备的总线地址来读取任何输入。信号通过与多路复用器和通信电路一起工作的发送/接收门进入FSK通信电路。图2-3显示了带有FSK多路复用器和FSK发送/接收门的FSK输入电路。解码数字输入后，FEC模块可以将数据存储在存储器中，或通过I/O扩展器总线接口将其直接发送到控制模块（MFP/MFC）。FEC模块可将-10至+10伏范围内的模拟值数字化。图2-4显示了模数转换电路。模数控制芯片提供控制双斜率积分器所需的逻辑。模数转换分为三个阶段：输入积分、与+10或-10伏参考电压的去积分以及将积分器/去积分器归零。微处理器向ADC电路发出信号，开始转换输入。ADC电路通过选择多路复用器选择输入、参考电压和转换操作。来自选择多路复用器的输入信号通过缓冲器和将输入信号转换为单端电压的差分放大器。然后信号到达积分器/去积分器级的输入。
I/O扩展器总线接口电路
FEC模块使用半定制门阵列作为I/O扩展器总线接口。集成电路（IC）保存所有控制逻辑和通信协议。该IC电路提供以下功能：•地址比较和检测。•功能代码锁存和解码。•读取选通生成。•总线信号的数据线滤波。•板载总线驱动器。ADC电路为该级选择正或负参考电压。一旦积分器设置为零，ADC电路允许积分器运行，直到其输出达到参考电压。此时，ADC电路选择去积分操作并开始计数，直到过零电路检测到信号为零。反馈和归零放大器将积分器设置为零，并且该过程以输入和参考电压的相反极性重复。ADC电路在去积分操作期间进行的计数是输入的数字等效值。它将信息和极性发送给微处理器。微处理器将其放入存储器，并向ADC电路发出信号以开始下一次转换。
FSK INPUTS (FIELD BUS MODE)
IMFEC11 ONLY For IMFEC11 modules in the field bus mode, all data and communication are FSK encoded digital signals on a shared bus and require decoding. The microprocessor can read any input by specifying the bus address of the device. The signal enters the FSK communication circuitry through a transmit/receive gate that works with the multiplexer and communication circuitry. Figure 2-3 shows the FSK input circuit with the FSK multiplexer and FSK transmit/receive gate. After decoding the digital input, the FEC module can store that data in memory or send it directly to the controlling module (MFP/MFC) through the I/O expander bus interface.The FEC module can digitize analog values within the range of -10 to +10 volts. Figure 2-4 shows the analog-to-digital conversion circuitry. The analog-to-digital control chip provides the logic needed to control the dual slope integrator. The analog-to-digital conversion takes place in three stages: input integration, de-integration with a +10 or -10 volts reference and zeroing the integrator/de-integrator.The microprocessor signals the ADC circuitry to begin converting inputs. The ADC circuitry selects the input, reference voltage and conversion operation through the select multiplexer. The input signal from the select multiplexer passes through buffers and a differential amplifier that converts the input signal to a single ended voltage. Then the signal goes to the input of the integrator/de-integrator stage.
I/O Expander Bus Interface Circuitry
The FEC module uses a semicustom gate array for the I/O expander bus interface. An integrated circuit (IC) holds all the control logic and communication protocol. This IC circuit provides the following functions: • Address comparison and detection. • Function code latching and decoding. • Read strobe generation. • Data line filtering of bus signals. • On-board bus drivers.The ADC circuitry selects a positive or negative reference voltage for this stage. Once the integrator is set to zero, the ADC circuitry allows the integrator to run until its output reaches the reference voltage. At this point, the ADC circuitry selects the de-integration operation and begins a count until the zero crossing circuit detects the signal at zero. A feedback and zeroing amplifier sets the integrator to zero and the process repeats with the opposite polarity of the input and reference voltage. The count that the ADC circuitry takes during the de-integration operation is the digital equivalent of the input. It sends that information and the polarity to the microprocessor. The microprocessor places it into memory and signals the ADC circuitry to begin the next conversion.
