51 single-chip microcomputer has high integration degree, strong control and processing capability, reliable and stable operation, and has been widely used in the fields of automatic detection of production processes, industrial real-time control, robotics, communication, navigation, medical and health, and intelligent instrumentation. In these applications, especially in the automatic testing and analysis of engineering signals, it is often necessary to record and store a large amount of data, and some data needs to be stored for a long time or permanently. At present, the tool for saving and recording data in a single chip microcomputer system is a random access memory (RAM). As we all know, RAM can't save data for a long time. The data memory of 51 series MCU system is only 64 KB at most, so these methods can't meet the requirements of some actual systems. The current magnetic recording technology is very mature, and hard disk recording and storage systems have become mainstream devices in computer systems. It has a large storage capacity and high access speed, which can permanently save data, but the price is getting lower and lower. Applying it to a single-chip microcomputer system can greatly improve the performance of the composed system.
The IBM-PC computer supports the hard disk system, and the interface technology between the host and the hard disk has been standardized and has been widely used. The hard disk system of IBM-PC is used as the data storage device of the 51 series single-chip microcomputer system. The interface circuit structure is simple, and there is no need to specially design the drive circuit of the hard disk, so the application system performance price ratio is very high.
First, the design of the interface circuit
The IBM-PC hard drive adapter is referred to as the hard disk controller. It is a smart component that can be connected to one or two hard drives and connected to a PC via a 62-pin I/O channel slot on the system board. The 62-pin signal line uses only 40 pins here, of which AO~A19 are 20-bit address lines; DO~D7 are 8-bit data lines; MEMR is used to read the basic I/O program of the hard disk; IOR and IOW are respectively host Read and write the control signal of the hard disk controller; IRQ5 and DRQ3 are the interrupt request and DMA request signal of the hard disk controller respectively; DACK3 is the signal sent to the controller when the host responds to the DMA; there is also a RESET signal for resetting the hard disk controller An AEN signal that prohibits I/O operation and six power and ground lines during DMA data transfer. The host reads data from or writes data to the hard disk by writing commands and control words to the six accessible registers provided to the hard disk controller. Therefore, when designing the interface circuit between the single chip microcomputer and the hard disk controller, it is only necessary to consider the generation and reception of the above signals, the expansion of the data memory of the single chip microcomputer, and the connection of the DMA controller. In the PC, the six accessible registers of the hard disk controller occupy the host's I/O port address 320-323H, and the signal transmission and reception are addressed through these port addresses. The 20 address lines actually use only 10, and the 51 series MCU has 16 address lines, which can meet the requirements of address decoding. The 51 series MCU does not directly support the DMA data transfer mode, and the data between the hard disk controller and the data memory must be DMA. In the PC, the read/write operation of the host to the hard disk controller is realized by reading/writing the I/O port, and the MCU system does not have an I/O read/write command, and the memory mapping mode can be used to The controller's four addresses are mapped to the external data memory, so that the controller's IOR and IOW are connected to the WR and RD of the microcontroller. The interrupt request signal IRQ5 of the hard disk controller is only used for the hard disk operation end signal. Therefore, this signal is used as the INT1 of the microcontroller. The connection mode of other signal lines is not described here. The interface circuit is shown in Figure 1-91.
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