| Rev |
Log message |
Author |
Age |
Path |
| 244 |
Added two new generics to the CPU model. The first is a supervisory mode that disables the STP PSR_I instruction. This prevents errant code execution from setting the I bit, and disabling any subsequent memory protection logic. The second allows the default state of the I bit to be set at startup. If set true, initialization code will run with the I bit set, allowing it to bypass memory protection.
Also modified the RAM models to include write mask logic, where the mask register is write-protected by the I bit in the CPU. When enabled, the models will prevent code from writing to memory regions which do not have their mask bits set. The upshot is that code can effectively "write protect" the RAM - which is useful for multitasking applications.
Also, most modules have been updated with write qualification inputs, allowing a similar scheme to be used for I/O, though not as elegantly. I use a register module, whose own write qual line is attached to the external copy of the I bit as an I/O write protect register.
Lastly, added a new externally triggered timer, which can generate pulses with programmable delays and widths, and which can interrupt on either the input trigger, the output rising edge, or output falling edge. The time base can be either the internal microsecond tick signal, or an external clock. |
jshamlet |
1640d 08h |
/open8_urisc/trunk/VHDL/o8_rtc.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 |
1674d 15h |
/open8_urisc/trunk/VHDL/o8_rtc.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 |
1675d 08h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 217 |
Broke out the vdsm8 as a separate entity, since it is used in several places,
Even MORE code cleanup. |
jshamlet |
1676d 09h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 213 |
Code and comment cleanup |
jshamlet |
1680d 10h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 211 |
Ok, this time with feeling. Timer should now properly reset on interval update. |
jshamlet |
1681d 14h |
/open8_urisc/trunk/VHDL/o8_rtc.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 |
1681d 16h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 209 |
Fixed an issue in the PIT timer that caused an immediate interrupt on interval write,
Fixed an issue in the epoch timer that resulted in a spurious interrupt due to extra LSB's being set by default in the set point register,
While cleaning elsewhere, founding a spacing issue in the CPU HDL,
Added a 4k ROM and MW core. |
jshamlet |
1682d 05h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 194 |
Cleaned up licensing sections |
jshamlet |
1690d 11h |
/open8_urisc/trunk/VHDL/o8_rtc.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 |
1690d 11h |
/open8_urisc/trunk/VHDL/o8_rtc.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 |
1702d 09h |
/open8_urisc/trunk/VHDL/o8_rtc.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 |
1703d 10h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 177 |
Fixed comments in RTC module |
jshamlet |
3035d 12h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 176 |
Fixed documentation errors,
Modified uSec_Tick such that it is always generated regardless of the interval. |
jshamlet |
3040d 10h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 172 |
General code cleanup |
jshamlet |
3235d 09h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
| 168 |
Simplified write data path logic,
Converted RTC to packed BCD,
Corrected several bugs in real time clock component, |
jshamlet |
4069d 06h |
/open8_urisc/trunk/VHDL/o8_rtc.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 |
4077d 05h |
/open8_urisc/trunk/VHDL/o8_rtc.vhd |
