The company said it will continue support for its current Z8 Encore! The devices are designed to meet the needs of designers working on consumer and. Microcontroller (MCU) Develop- because our kit then serves as your complete Z8 Encore!® additional cost allowing you to begin your design immedi- ately. What would be better than designing a softcore to learn more about VHDL ( VHSIC hardware I ended up choosing a modern Z relative: the Zilog Z8 Encore!.

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Regarding the instruction set, there are 83 different instructions split into two opcode pages.

With its lightweight IDE integrated development environment and free ANSI C compiler, it is an excellent project to learn and also teach about embedded systems. With an instruction queue; that is, a mechanism that keeps fetching bytes from program memory and storing them into an eight-byte array:. After a couple hours, I came up with the current design. It comprises usual instructions for basic operations such as addition, subtraction, logical operations, data manipulation instructions, shifting instructions, change-of-flow instructions, some bit instructions, bit testing and manipulation, 8×8 multiply, etc.

Building Your Own Microcontroller

The decoder stage uses this number to verify that the desired number of bytes for the instruction is already available in the queue. The design makes use of a nested IF chain which generates a vector address upon detection of an interrupt event regarding an enabled interrupt. Encoore feature replaces having a traditional microcontroller implementation of Back EMF sensing using an extra comparator and multiplexer, thus saving die area and PCB space.

Note that I am not using bidirectional buses for any interconnects in this project. Before connecting, make sure that debugger settings are the same as in Figure 8.

Zilog offers a high-end, ICE in-circuit emulator kit, which includes package adapters and event trace functions. In many applications, electrical noise generated by the motor can interfere with the microcontroller’s operation.


After a lot of tests and some Googling, I figured out that it was possibly related to the asynchronous edges of the serial input signal. Once the code is successfully downloaded, you can start the application GO buttonstep instructions, inspect or edit registers, set breakpoints, etc.

Embedded Insights – Embedded Processing Directory – Zilog Z8 Encore! MC

I then included a cascaded latch to synchronize the signal to my internal clock and all the problems were gone! In the beginning, some temporary variables are initialized to a default condition. The Back EMF signal is locked from the very onset of the start-up phase, without the need for initial placement of the rotor in a specific position. So, we can design an ALU which takes a qith as input the higher nibble from the opcode and decodes it accordingly. If we look at row 0x1, we can see that columns 0x0 and 0x1 are RLC instructions, and columns 0x2 up to 0x9 are ADC instructions.

MC, the microcontroller uses a highly accurate Internal Precision Oscillator as the system clock source one of a number of system clock options to aid in noise reduction. The queue counter CNT is used to identify the number of bytes available for use reading in the queue.

This was inwhen I had more contact with programmable logic and VHDL and my curiosity was peaked. In the Z8 Encore! One last comment regarding interrupts: Checking the timing analysis messages, I could see a warning that the maximum clock should be around 24 MHz.

I then used a divider-by MC which eliminates the need for an external comparator. This is where the decoder actually decodes the opcodes, prepares buses and internal supporting signals, and steps to other execution states. Fetching instructions is a primary task for any CPU. These multi-part series may be just what you need! The eZ8 core also includes a vectored interrupt controller with programmable priority and an on-chip debugger which communicates with the host computer using asynchronous serial communication.


Table 1 shows program memory organization. Its value is used in the last part of this stage to increment the PC program counteradvance the queue read pointer, and decrement the number of available bytes in the queue. That means the CPU can fetch a new instruction while another is reading or writing into data memory.

Zilog Document Download

The five register area buses comprise three for the file register area user RAMand another two dedicated to microconfroller function registers. Aith instruction decoder reads opcodes from the instruction queue and translates them into corresponding operations.

Once fully compiled I used Quartus II v9. While this would work for columns 0x2 to 0x9, we would need another approach for the first two columns. Just ignore the warning and proceed with the debugging session. To my surprise, while most of the time I could successfully send commands and receive the expected results, sometimes the design would simply freeze and stop responding. You can supply a hex file and use the MegaWizard Plug-in Manager to change the program encorre initialization file.

Learning Electronics Need to brush up on your electronics principles?

The eZ8 has a variable length instruction word instruction length varies from one byte up to five bytes ; some instructions are lengthy but run faster than others. This feature enhances motor performance and functionality without adding cost to the Bill of Material. Using the FPz8 is very simple and straightforward.