VHDL Source Code for eP32

2012 FIG Taiwan Conference

February 17, 2012

Chen-Hanson Ting

Summary

ep32_chip.vhd Overall Design ep32.vhd CPU of eP32 ram_memory.vhd Memory of eP32 uart.vhd Serial port gpio.vhd General purpose IO ep32q_tb.vhd Testbench

VHDL Souce code I will scan the source code files so we

have a general idea on what eP32 contains and how it is implemented.

VHDL code is very portable so that you can move it to any FPGA chip or ASIC chip.

eP32 is the simplest, yet most complete microprocessor design ever.

ep32_chip.vhd

Define all external connections Define ports of all components Define signals connecting all

components Instantiate all components

ep32.vhd

Define IO ports of CPU Define internal signals and registers

Define logic relations among signals Define instruction set Define finite state machine to

execute instructions

ram_memory.vhd Instantiate DQ RAM memory modules. Initialize RAM memory contents to a

FORTH dictionary. This module cannot be ported from one

FPGA to another. It must be generated by tools provided by specific FPGA IDE.

eP32 requires asynchronous RAM modules.

Memory is mapped to 0-$00001FFF.

uart.vhd Instantiate a Universal Asynchronous

Receiver Transmitter (USART). USART is initialized to 115,200 baud,

1 start bit, 8 data bits, 1 stop bit, no parity, and no flow control. It can be configures to other options.

USART registers are mapped to $8000000x.

gpio.vhd Instantiate a 16 bit general purpose

IO port. It includes these registers:

Direction Register Input Register Output Register

Registers are mapped to $E000000x.

ep32q_tb.vhd

It is required by ispLEVEL to simulate eP32 chip.

A template is provided by ispLEVEL. It is customized for eP32 chip.

DIAMOND does not need a testbench. Signals in the eP32_chip top module can be customized to drive eP32 chip.

Conclusion

CPU design is simple. Most CPU designers do not

understand computer, and made their designs unnecessarily complicated.

eP32 is the simplest, yet most complete microprocessor design ever.

莊子『庖丁解牛』良庖歲更刀，割也。族庖月更刀，折也。今臣之刀十九年矣，所解數千牛矣，而刀刃若新發於硎。彼節者有閒，而刀刃者無厚，以無厚入有閒，恢恢乎其於遊刃必有餘地矣。