A 32-Bit Computer for LatticeXP2 Brevia Development Kit

Report
VHDL Source Code for eP32
2012 FIG Taiwan Conference
February 17, 2012
Chen-Hanson Ting
Summary
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ep32_chip.vhd
ep32.vhd
ram_memory.vhd
uart.vhd
gpio.vhd
ep32q_tb.vhd
Overall Design
CPU of eP32
Memory of eP32
Serial port
General purpose IO
Testbench
VHDL Souce code
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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
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Define all external connections
Define ports of all components
Define signals connecting all
components
Instantiate all components
ep32.vhd
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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
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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
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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
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Instantiate a 16 bit general purpose IO
port.
It includes these registers:
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Direction Register
Input Register
Output Register
Registers are mapped to $E000000x.
ep32q_tb.vhd
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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
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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。

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