Design of Single Chip Microcomputer Simulator Based on SST89C54/58

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Design of Single Chip Microcomputer Simulator Based on SST89C54/58 [Copy link]

1 Overview

SST89C54/58 (abbreviated as 89C54/58) is a multi-purpose 51 series microcontroller launched by SST Corporation of the United States. It integrates 20 kB/36 kB SuperFlash E'PROM program memory in the chip, which is divided into two blocks: BLOCK0 (16 kB/32 kB) and BLOCK1 (4 kB). Among them, BLOCK1 can be mapped to the highest or lowest end of the 64 kB storage space, and it can be invisible to the program counter. Due to its unique advantages in storage structure, 89C54/58 is very suitable for use as a microcontroller emulator.

2 Program storage structure of SST89C54/58

2.1 Memory structure

The storage block BLOCK0 in the 89C54/58 chip occupies the storage space from 0000H to 3FFFH/7FFFH, and BLOCK1 occupies the storage space from F000H to FFFFH. The storage structure of 89C54/58 is shown in Figure 1.

When EA#=1, BLOCK0 is always visible to the program counter for code access; BLOCK1 code access is achieved through special function registers SFCM, SFCF, SFAL, SFAH, SFDT and SFST. When SFCF[7]=1, BLOCK1 is visible.

2.2 Memory Remapping

The memory remapping function of 89C54/58 allows the system interrupt vector area to be still available when programming BLOCK0 (ordinary 8051 series microcontrollers do not have this feature). 89C54/58 provides four memory remapping methods. The size of the memory remapping number is controlled by MAP_ENCl: 0. When MAP-


3 Design of microcontroller emulator based on SST89C58

3.1 Design principle introduction

The emulator circuit design is shown in Figure 2. In the figure, U2 is the serial communication interface chip MAX232, and U1 is 89C54/58. The monitoring program of 89C54/58 communicates with KEILC51 through the serial port of the PC to realize the real-time simulation function.

3.2 Loading of the emulator monitoring program

The 89C54/58 emulator monitoring program SoftlCE (Softwareln-CircuitEmulator) provided by SST can be loaded through the BSL (Boot-StrapLoader) provided by SST or written through a third-party programmer that supports SST89C54/58.

3.3 Introduction to the performance of the emulator

The 89C54/58-based MCU emulator has all the functions of a general emulator except that it does not support serial port emulation. Combined with KEIL software, it can complete the emulation design of most MCU application systems.

Its specific performance is as follows:

(1) Can download Intel HEX format files.
(2) Support assembly and C51 source code debugging.
(3) Support online assembly.
(4) Support single-step (Step) function.
(5) Support step-over (StepOver) function.
(6) A maximum of 10 fixed breakpoints and one temporary breakpoint can be set.
(?) Support reading and writing data memory.
(8) Support reading and writing program memory.
(9) Support reading and writing special function registers.
(10) Support reading and writing ports.
(11) Has IAP (1n-Application Programming) function.

3.4 KEIL Software and Settings

KEIL C51 is a Windows version of the 8051 series microcontroller development kit launched by KEIL of Germany. It can be used to compile C source programs, assemble source programs, link and locate target files and libraries, create HEX files, and debug target programs. It is also embedded with the RTX51 real-time operating system, which can simplify the design of complex multi-task real-time application systems. When used with the 89C54/58 emulator, the settings in the KEIL development environment are as follows:

(1) Create a project and select the SST microcontroller SST89C54/58.
(2) Select "Options for, Target 1/" from the menu.
(3) In the "Options for Target, Target 1" window, select to use KEIL Monitor-51 Driver, as shown in Figure 3.
(4) Double-click the Settings button in Figure 3, set the target parameters as shown in Figure 4, and then compile and debug the target program.

4 Conclusion

In summary, due to the unique memory structure of SST89C54/58, 89C54/58 can be used as a general-purpose 51 microcontroller and can be made into a 51 series microcontroller emulator with only a small amount of peripheral circuits. Combined with the powerful KEIL software, it provides a real-time simulation development environment for microcontroller engineers and can complete the design of most microcontroller application systems. Detailed design information can be downloaded from the SST company website ( www.sst.com ).