With the Zilog Z80 microcontroller’s end-of-life (EOL) date looming, Z80 lovers eagerly search trendy alternate options for his or her Z80-based computer systems. The eZ80, with its binary-compatible mode and ongoing manufacturing, presents a promising answer. Nonetheless, it isn’t a easy drop-in alternative. So, Dean Netherton took up the problem of designing an eZ80 CPU card appropriate with the RC2014 pc and bus normal.
Launched by Zilog in 2001, the eZ80 microprocessor (MPU) adopted the unique Z80 microcontroller, which powers many 8-bit computer systems. The eZ80 can function at increased speeds, boasts a spread of newer peripherals, and has a binary compatibility mode. Not like its discontinued predecessor, the eZ80 remains to be an energetic product. Netherton selected the eZ80F92 for the eZ80 CPU card challenge. This processor operates as much as 20 MHz with 128 KB of on-chip Flash and eight KB of RAM.
The RC2014 is a modular pc based mostly on the Zilog Z80. It’s not a clone of a particular pc however a contemporary creation. One distinctive attribute is that there isn’t a motherboard. As a substitute, the RC2014 bus module specification calls out the design necessities for a bus that modules plug into, together with the CPU card.
eZ80 CPU module (📷: Dino Boards)
The eZ80F92’s 100-pin LQFP bundle pushed Netherton’s restricted surface-mount soldering talents, however improved soldering abilities had been one of many challenge’s aims! The ultimate eZ80 CPU card took 4 iterations to realize. The ultimate four-layer card comprises the MPU, passive parts, a crystal for the on-chip RTC, and pins to hook up with a service board.
Netherton wanted a backplane adapter PCB to be used with a pc just like the RC2104. This board comprises appropriate pin sockets for the eZ80 CPU module, an oscillator, 74HCT245 buffers, and the right-angle header pins to hook up with the RC2014 bus. There are extra interfaces damaged out from the eZ80. For instance, the UART header can ship knowledge from the MPU at 115200 baud.
As with most initiatives, blinking LEDs are sometimes a primary milestone. Netherton efficiently demonstrated that the eZ80 module connected to the backplane adapter may drive LEDs on a peripheral card additionally plugged into the RC2014 bus. It’s a small demo however an vital one.
The eZ80 runs firmware to handle its start-up, configure on-chip gadgets, deal with interrupts, and eventually change into Z80 compatibility mode. You will discover the firmware on this GitHub repository. To construct the firmware, you’ll need the Zilog ZDS IDE and a 6-pin Zilog Good Cable adapter. This proprietary interface can flash, management, and debug the MPU.
eZ80 module on interface PCB (📷: Dino Boards)
Take a look at the Dinoboards eZ80 for the RC2014 backplane challenge web site for extra data. It comprises challenge logs and schematics.