| Rev |
Log message |
Author |
Age |
Path |
| 194 |
Cleaned up licensing sections |
jshamlet |
1715d 14h |
/open8_urisc/trunk/VHDL/o8_cpu.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 15h |
/open8_urisc/trunk/VHDL/o8_cpu.vhd |
| 190 |
Fixed a bug in CPU where RTI/RTS wasn't idling the instruction cache, causing intermittent failures where RTI would execute as RTS, corrupting the stack;
Fixed a bug in the real-time clock where the uSec tick generator would stop if the PIT timer value was left/set to 0x00. |
jshamlet |
1727d 13h |
/open8_urisc/trunk/VHDL/o8_cpu.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 16h |
/open8_urisc/trunk/VHDL/o8_cpu.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 12h |
/open8_urisc/trunk/VHDL/o8_cpu.vhd |
| 186 |
Merged the interrupt override logic into the case structure, simplifying how interrupts are processed. |
jshamlet |
1733d 12h |
/open8_urisc/trunk/VHDL/o8_cpu.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 15h |
/open8_urisc/trunk/VHDL/o8_cpu.vhd |
| 183 |
Renamed core to o8_cpu to match new naming scheme |
jshamlet |
1735d 15h |
/open8_urisc/trunk/VHDL/o8_cpu.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 15h |
/open8_urisc/trunk/VHDL/Open8.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 11h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 172 |
General code cleanup |
jshamlet |
3260d 13h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 169 |
Corrected issue with CMP and SBC generating an inverted carry flag and added new constants to the package file to simplify interfacing new modules. |
jshamlet |
3315d 14h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 168 |
Simplified write data path logic,
Converted RTC to packed BCD,
Corrected several bugs in real time clock component, |
jshamlet |
4094d 10h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 167 |
Updated CPU model; Pipelined ALU control signals to improve fMAX, corrected issue with interrupt controller priority not being obeyed, fixed bug in auto-indexing instructions where the upper register wasn't being properly incremented, cleaned up code to make the processor model easier to follow.
Added several useful modules that use the Open8 bus. |
jshamlet |
4102d 08h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 164 |
Modified the data path to allow the bus to go idle while waiting for an interrupt. This makes it easier to debug code that uses the WAI instruction, as both Wr_Enable and Rd_Enable go low. |
jshamlet |
4738d 04h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 162 |
Added optional generic to specify that the BRK instruction implements a WAit_for_Interrupt (WAI) instruction instead. Logically emulates INT, but without triggering a soft interrupt. Note that the NOP instruction maps to BRK, and will not function correctly if this option is set. |
jshamlet |
4828d 21h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 156 |
Optimized for timing,
Flattened block structure to single entity. |
jshamlet |
4885d 12h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 155 |
Fixed additional interrupt logic bug,
Optimized several blocks - including ALU, stack, program counter, and data path. |
jshamlet |
4886d 07h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 154 |
Fixed problem with missing data path override in interrupt logic. Should resolve issues with processor crashing when an interrupt occurs as a STO instruction is being executed. |
jshamlet |
4891d 09h |
/open8_urisc/trunk/VHDL/Open8.vhd |
| 153 |
Fixed bug in interrupt logic that caused stack pointer to increment if interrupt occurred as specific instructions were being decoded,
Fixed bug in interrupt logic where instruction caching would remain enabled during an interrupt, causing improper execution depending on what instruction was in the decode stage as the interrupt is trigered. |
jshamlet |
4918d 05h |
/open8_urisc/trunk/VHDL/Open8.vhd |
