D DMA（直接内存访问） Direct Memory Access. A technique for transferring data directly between two peripherals (usually memory and an I/O device) with only minimal intervention by the processor. DMA transfers are managed by a third peripheral called a DMA controller. 直接内存访问。一种直接在两个外设（通常是内存和I/O设备）之间进行数据传输的技术，它只要处理器最少的介入。DMA传输由叫DMA控制器的第三方外设进行管理。

 

 DRAM（动态随机访问存储器）

Dynamic Random-Access Memory. A type of RAM that maintains its contents only as long as the data stored in the device is refreshed at regular intervals. The refresh cycles are usually performed by a peripheral called a DRAM controller. 动态随机访问存储器。一种RAM，存储在其设备中的数据被定期刷新时才能保存它的内容。刷新周期一般由一个叫DRAM控制器的外设完成。

 

 Data bus（数据总线）

A set of electrical lines connected to the processor and all of the peripherals with which it communicates. When the processor wants to read (write) the contents of a memory location or register within a particular peripheral, it sets the address bus pins appropriately and receives (transmits) the contents on the data bus. 连接处理器与所有外设进行通讯的电子线路集。当一个处理器想去写（读）某一特定外设中的存储器地址或寄存器中的内容时，处理器设置地址总线并在数据总线上接收（传输）内容。

 

 Deadline（死线）

 The time at which a particular set of computations must be completed. See also real-time system. 一个特定计算必须被完成的时间。请看实时系统。 Deadlock（死锁）

An unwanted software situation in which an entire set of tasks is blocked, waiting for an event that only a task within the same set can cause. If a deadlock occurs, the only solution is to reset the hardware. However, it is usually possible to prevent deadlocks altogether by following certain software design practices. 一种不希望出现的软件状态，在这个状态下，所有的任务因为等待一个只有在这些被阻塞任务之一才能产生的事件而被阻塞。如果死锁发生，唯一解决的方法是重启动硬件。但是，通过可靠的软件设计实践活动通常可以防止死锁的发生。

 

 debug monitor（除错监视程序）

 A piece of embedded software that has been designed specifically for use as a debugging tool. It usually resides in ROM and communicates with a debugger via a serial port or network connection. The debug monitor provides a set of primitive commands to view and modify memory locations and registers, create and remove breakpoints, and execute your program. The debugger combines these primitives to fulfill higher-level requests like program download and single-step. 嵌入式软件被特殊设计来作为除错工具的一部分。它一般被放在ROM中，通过串口或网络与除错器进行通讯。除错监视程序提供一个简单的命令集来显示和内存地址和寄存器、建立和移除断点，并且运行你的程序。除错监视器组合这些简单的命令去实现象程序下载各单步调试等高端的请求。