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[/] [open8_urisc/] [trunk/] [VHDL/] [Open8_pkg.vhd] - Rev 313

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313 Added all generics to package component jshamlet 572d 23h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
270 Moved CPU internal constants to o8_cpu.vhd and replace the generic that set the RSP direction flag with a constant instead. This removes the need to expose internal architectural flags externally.

Also added a hard-coded version register that takes a major and minor value as bytes using generics. This is a read-only register to the CPU.
jshamlet 1509d 20h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
269 Modified the write data path to use separate enumerated states rather than reuse the .reg field to improve performance. jshamlet 1512d 09h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
251 Added RAM write fault detection, which can be used to indicate a memory write violation by the CPU. This allows a clean shutdown in the event of a memory problem/program crash.

Fixed a bug in the status_led.vhd entity that kept the flashing light function from working. The new code uses a maximal length 24-bit LFSR to create long delays. This is more efficient than a binary counter, but results in non-exact frequencies as a function of SYSTEM_FREQUENCY / (2^24-1).

Added the ability to use unsigned offsets to the LDO/STO instructions. The original behavior of signed offsets is preserved if the Unsigned_Index_Offsets is left unset or set to FALSE. While inserting this code, pipeline registers were also inserted into the address generation logic for indexed instructions. This simplifies the final multiplexor and improves FMax at the slight expense of LDO/SDO now taking one additional clock cycle to execute.
jshamlet 1645d 16h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
228 Added an initialization constant for the OPEN8_BUS_TYPE record. jshamlet 1699d 11h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
227 Added a demonstration Open8_cfg.vhd file, which is used to configure the system constants. It also provides a function that makes it easy to merge read buses. jshamlet 1699d 18h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
226 Forgot the updated package file... jshamlet 1699d 22h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
224 Finished new Open8 bus record, which now includes the clock, reset and a microsecond tick. The CPU now accepts a clock and pll_locked signal, which it uses to generate the system reset in the bus record. It also contains a simple microsecond counter to feed the usec_tick in the record. This logic was removed from the real time clock and system timer entities, which now use the global version. Bus connections should be dramatically simplified, as only the read logic and interrupts are still run as separate signals. jshamlet 1700d 00h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
223 Added an OPEN8_BUS_TYPE record to simplify connection to Open8 modules. The CPU now passes and Open8_Bus out, which supplies the bus address, write enable, write data, and read enable. Read data and interrupts are still handled as separate signals, since they are muxed/connected at the next level up. jshamlet 1700d 17h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
220 More revision sections added jshamlet 1701d 17h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
210 Modified the timers to reset on new interval write. This avoids an issue in the original design where the timer had to reach zero before updating, potentially causing unwanted interrupts.
Also added a flag to the CPU to allow interrupts to be processed sequentially based on the state of the I bit. This one is set to false by default, as it is a significant change in interrupt behavior. Long, and reentrant, ISRs can clear the I bit prematurely to allow themselves to be interrupted.
Lastly, added the I bit to the exported flags for possible use in memory protection schemes.
jshamlet 1707d 01h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
191 Cleaned up comments, added back the OPEN8_NULLBUS constant, and added some new modules for ADCs and LCD displays.
Also made the button input module more configurable by moving the debounce code to a separate entity and using generics to instantiate it.
jshamlet 1715d 20h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
189 Merged changes from private repository,
added ceil_log2 function to Open8_pkg, since it is used to calculate RAM vectors,
cleaned up comments and removed local copies of the ceil_log2 function from peripherals.
jshamlet 1728d 19h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
188 Added a generic to alter the behavior of RTI so that it can optionally skip restoring the general purpose flags GP4 to GP7, allowing ISR's to make persistent changes to them. Also exported these flags to the top level for use outside the CPU. jshamlet 1728d 21h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
187 Added the CPU_Halt input, only now as an input to the instruction decoder. The CPU_Halt line will assert the registered CPU_Halt_Req, which will cause the instruction decoder to abort the current instruction, reset the PC, then enter a hold state until the line is deasserted. Additionally, a very minor bug that could cause the SMSK instruction to effectively execute twice if interrupted was fixed. Lastly, cleaned up the comments even more. jshamlet 1730d 18h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
186 Merged the interrupt override logic into the case structure, simplifying how interrupts are processed. jshamlet 1733d 17h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
185 1) Fixed an apparently long-standing bug where the interrupt bit wasn't being cleared after an RTI
2) Modified the program counter logic to be simpler. It now always increments, and states control the increment using the offset field. A new set of constants was added to replace the old states.
3) Modified the ALU to always use Operand1 instead of ALU_Ctrl.Data (and removed the field in the record). A new ALU command, ALU_GMSK, was added, as it was the only instruction to set the .Data field to something other than Operand1 (Int_Mask)
4) Modified the package file so that flag names match what the assembler calls them. FL_Z is now PSR_Z, FL_GP1 is now PSR_GP4, etc.
5) Cleaned up the comments and code formatting
jshamlet 1733d 20h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
183 Renamed core to o8_cpu to match new naming scheme jshamlet 1735d 20h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
182 Simplified the address generation logic at the expense of making LDX take one additional clock cycle. This allowed the address logic to be split out of the main state machine and simplified (greatly). During this process, a bug in SDO was found and fixed that caused it to return through the wrong pipe fill state wnen auto increment was disabled. jshamlet 1735d 20h /open8_urisc/trunk/VHDL/Open8_pkg.vhd
181 Altered the RSP instruction to allow the stack pointed to either be restored from registers or stored to registers based on the status of a processor bit. Also modified LDX to simplify the address logic. jshamlet 1736d 17h /open8_urisc/trunk/VHDL/Open8_pkg.vhd

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