英文文献-基于单片机的大棚温湿度控制系统的设计

英文文献-基于单片机的大棚温湿度控制系统的设计内容摘要：

ividual bits of memory or I/O since many controller applications involve the turning on and off of single output lines or the reading the single line. These lines are readily interfaced to twostate devices such as switches, thermostats, solidstate relays, valves, motor, etc. Parallel input/output. Parallel input and output schemes vary somewhat in different microputer。 in most a mechanism is provided to at least allow some flexibility of choosing which pins are outputs and which are inputs. This may apply to all or some of the ports. Some I/O lines are suitable for direct interfacing to, for example, fluorescent displays, or can provide sufficient current to make interfacing other ponents straightforward. Some devices allow an I/O port to be configured as a system bus to allow offchip memory and I/O expansion. This facility is potentially useful as a product range develops, since successive enhancements may bee too big for onchip memory and it is undesirable not to build on the existing software base. Serial input/output . Serial munication with terminal devices is mon means of providing a link using a small number of lines. This sort of munication can also be exploited for interfacing special function chips or linking several microputers together .Both the mon asynchronous synchronous munication schemes require protocols that provide framing (start and stop) information .This can be implemented as a hardware facility or U(S) ART(Universal(synchronous) asynchronous receiver/transmitter) relieving the processor (and the applications programmer) of this lowlevel, timeconsuming, detail. t is merely necessary to selected a baudrate and possibly other options (number of stop bits, parity, etc.) and load (or read from) the serial transmitter (or receiver) buffer. Serialization of the data in the appropriate format is then handled by the hardware circuit. Timing/counter facilities. Many。