Abstract: This paper introduces a small-format paperless recorder developed while maintaining compatibility with medium-format paperless recorders. This recorder features a fully Chinese graphical interface, universal input, and comprehensive functions, utilizing new technologies such as data space expansion pagination access management and code space expansion switching. The implementation of these new technologies is discussed in detail from both hardware and software perspectives. Keywords: Pagination access, code switching, paperless recorder. Recorders are common secondary instruments in industrial production automation systems. Traditional recorders have limited functionality, are prone to mechanical failures, and require cumbersome daily maintenance, making them unable to meet the requirements of comprehensive automation in production processes. The color medium-format paperless recorder developed by the author in 1998 has been commercialized and widely used in process monitoring in the chemical and steel industries, receiving positive feedback from users. Based on this, and according to actual user needs and feedback, the author has developed a new generation of color small-format paperless recorders. The recorder has a 5" DSTN color LCD display, 1-8 channels of universal input, 16 alarm points, and 2 PID output points. It is small in size, full in function, and can meet the needs of most industries. 1 Main functions (1) Signal sampling: Analog input channels 1-8. Fully isolated universal input, can input 0-10V, 0-5V, 0-10mA, 4-20mA standard signals and PT100, Cu50 thermal resistance signals as well as K, S, B, N, T, E, J, R thermocouple signals. Users can directly select on the configuration screen without changing the input channel board. The recording interval can be set to 1/2/4/8/20/40/60/120/240, etc. (2) Configuration function: The recorder has powerful configuration function. Users can set the channel signal type, unit, range, display range, recording interval, alarm upper and lower limits, as well as display screen, historical memory, flow accumulation, PID parameters, etc. The graphical configuration interface is easy to operate. (3) Display function: Full Chinese graphical interface, menu-driven, intuitive and rich information, simple operation. Main display screens: horizontal trend screen, vertical trend screen, bar chart screen, digital screen (all of the above screens can be selected from 1 to 8 channels), historical digital trend recall screen (single channel or multiple channels simultaneously), multi-channel flow accumulation screen, configuration screen (including channel settings, display settings, flow accumulation settings, PID parameter settings, historical recall settings, etc.). (4) Storage function: Uses large-capacity Flash as the main storage device (users can choose 1/2/4/6M). Floppy disk is used as an auxiliary device. Users can transfer data within any time period to the floppy disk and then display, analyze, and print it on the PC. (5) Communication function: Provides RS-232/RS-485 communication interface. It can communicate over long distances and network multiple instruments. With the help of the host PC software, remote monitoring can be realized. (6) Printing function: Provides common micro printer interface to print data, trend curves, flow accumulation values, etc. within any time period. (7) Alarm function: Equipped with 16-point switch output channels (selectable always open/always closed), the alarm signal is output while the alarm information is displayed on the screen in real time according to the upper and lower limits set for each channel. (8) Simple PID adjustment function: It has two PID output channels with signal types of 1～5～/4～20mA. 2 Hardware Design The color medium-length graph paperless recorder previously developed by the author adopted a host computer structure. The host computer uses an ALL-IN-ONE type PC104 embedded template as the hardware platform, directly connected to a GB-level hard disk and a 1.44MB floppy disk, a 10" color TFT LCD screen with a resolution of 640×480, and a 6-key numeric keypad. The slave computer uses a data acquisition module with PHILIPS 80C552 as the control core. The host computer is responsible for screen display, user configuration, data management, printing, and remote communication (RS232 or 485). The slave computer is responsible for signal conditioning, data calculation, alarm, and PID output. The host computer and slave computer are connected through an RS232 interface to transmit channel configuration information and channel data values. The structural block diagram is shown in Figure 1. The advantages of this structure are modular design, with each computer performing its own function and working collaboratively; flexible application and good compatibility; and high fault location capacity. The ease of use and reliability of this system have been proven in factory applications. However, it should also be noted that the functionality of the PC104 template is not fully utilized in this system, resulting in significant waste of hardware space (hard drives with capacities below 4GB are currently unavailable on the market), and the high price of the LCD screen contributes to the relatively high price of the recorder. After summarizing the development of the medium-length and long-diagram paperless recorder, the design of the small-diagram paperless recorder also adopts the upper and lower computer structure. The lower computer's data acquisition module is interchangeable with that of the medium-length and long-diagram paperless recorder, thus avoiding redundant development and making the small-diagram and medium-length and long-diagram paperless recorders a unified system. A new upper computer based on the DALLAS 80C320 was developed. The structural block diagram is shown in Figure 2. It employs a 5" DSTN color LCD screen with a resolution of 320×240. Data storage primarily utilizes high-capacity Flash memory, while auxiliary equipment uses 1.44M floppy disks, controlled by the GM82C765. The use of the 80C320 is based on two main considerations: First, the 80C320 has two UARTs, enabling communication between the recorder's internal upper and lower computers as well as remote communication with external devices, significantly reducing the complexity of software programming; second, the GM82C765 floppy drive controller has high real-time requirements, and the 80C320's 4-cycle technology allows it to execute instructions three times faster than other 51 microcontrollers using the same crystal oscillator. Furthermore, the dual DPTR structure improves program execution efficiency, thus better complementing the GM82C765. Because the LCD screen is driven by RAM, and the large-capacity parallel Flash memory far exceeds the 64K data addressing space of the 51 microcontroller, we expanded the data space of the 80C320 by adding 8 address lines. We implemented paging management (each page is 32K in size) for the increased address space, utilizing the original high-end 32K data space of the 51 for page swapping access. Within the increased data space, we allocated 32K of I/O space, 64K of LCD display space, and Flash memory space, expanding the data space to 8M. The schematic diagram is shown in Figure 3. For programming, the data space is the original 64K space. When the program needs to access the expanded data space, it first writes the high 8 bits of the address to address 0x7FFF for page selection. The hardware chip select circuit maps the selected page to the original high-end 32K data space of the 51. Subsequent access to the high-end 32K data space is equivalent to accessing the selected page in the expanded data space. The expanded data space is divided into a total of 256 pages. Access to the low-end 32K data space is not affected by page selection. Due to the limitations of the 51 series microcontroller architecture, its code space is only 64K. The software for the small long-map paperless recorder is written in C language, features a menu-driven, fully Chinese graphical interface, and is fully functional; however, the software code exceeds 64K. To solve this problem, we innovatively used an expanded code space and manually controlled chip selection to switch between code spaces. This can be considered a technological innovation in the smallest long-map paperless recorder. Its hardware principle is shown in Figure 4. In terms of software design, to ensure the program can freely switch between the two code spaces and guarantee normal operation, high requirements are placed on software writing, compilation, linking, and positioning. This is explained in detail in the software design section below. 3 The software design for the small long-diagram paperless recorder uses a hybrid C and assembly language. While C programming improves development efficiency and code quality, the current C51 compiler still has limitations in applications with high real-time requirements. Therefore, the main body of the software is written in C, while low-level functions such as accessing the GM82C765 floppy drive controller and driving the LCD screen are written in 51 assembly language. The connection between the C program and assembly language modules mainly addresses variable passing, sharing, and code calling. Due to space limitations, this will not be discussed further here; interested readers can refer to reference 3. A key issue to be addressed in the software design is code switching. Its schematic diagram is shown in Figure 5. The code for Function1 and Function2 in the schematic is quite large, exceeding the 64K limit when compiled in a single project. Therefore, they are placed in two separate code spaces. The corresponding program must be written as two separate projects. Function1 is placed in ROM1, and Function2 in ROM2. MainLoop and SwitchChip are common functions. To ensure correct compilation and linking, empty functions for Function2 and Function1 are added to ROM1 and ROM2 respectively. The code space switching process is as follows: Assume that after power-on, the program starts running in ROM1 space and enters the MainLoop loop to wait for events to occur. At a certain moment, event2 occurs, and the program calls SwitchChip with parameter 2 (see ① in the figure). After entering the SwitchChip function, the chip select is set according to the parameters, selecting ROM2. The program then runs in ROM2 space (see ② in the figure). The SwitchChip function returns and begins calling the actual Function2 function in ROM2 (see ③ in the figure). After completion, the program loops in the MainLoop in ROM2 space, waiting for new events to occur. When the program runs in the MainLoop of ROM2, event1 occurs, and the program calls SwitchChip with parameter 1 (see ④ in the figure). After entering the SwitchChip function, the chip select is set according to the parameter, first selecting ROM1, so the program returns to the ROM1 space to run (see ⑤ in the figure). The SwitchChip function returns and begins to call the actual Function1 function in ROM1 (see ⑥ in the figure). After execution, the program loops in the MainLoop of ROM1 space. When the program runs in ROM1 and event1 occurs, calling SwitchChip will not switch the ROM space, thus correctly calling the Function1 function. The same applies when event2 occurs in ROM2. From the schematic diagram and the above process, it can be seen that the necessary conditions for the correct switching between the two ROM spaces are: • The starting address of the MainLoop function in both ROMs must be the same, and the statements must be exactly the same, thus ensuring that the address of each statement is the same. • After ROM switching, the return address of the function call is the same. • The program can run normally without crashing. Similarly, the SwitchChip function bodies in both ROMs must be identical and located at the same address. The locations of global variables in RAM in both projects must be completely consistent; otherwise, unpredictable consequences will occur. The switching rate of the ROM chip select line must be fast enough so that the chip select signal stabilizes before the CPU reads the next instruction. The location of functions and variables in the program can be referenced from the location switches of the C51 compiler and linker, which will not be elaborated here. The design and development of the color small-format paperless recorder maintains the same universality as the color medium-format paperless recorder. The basic functions are the same, but the size is reduced, and the cost is lower. Furthermore, it utilizes new technologies such as extended RAM paging access management and extended ROM switching.