Rev |
Log message |
Author |
Age |
Path |
242 |
Added write protect logic to the RAM cores and system timer as part of scheme to keep tasks from messing up the scheduler or other task's memory. The RAM is now divided into regions with a separate write mask register. The write mask register itself is only writeable with the I bit is set (during an interrupt or by setting it using STP PSR_I). The 1K memory is divided into 16, 64 byte regions while the 4K memory is divided into 32, 128 byte regions. The system timer simply checks for the I bit being set when the write protect generic is set.
Note that setting the write_protect generic false, or leaving it unset, will keep the previous behavior. |
jshamlet |
1566d 10h |
/open8_urisc/trunk/VHDL/o8_sys_timer.vhd |
229 |
Created a new version of the system timer with 24-bit, 1-uS resolution. The new timer has a much different register interface, so it is now o8_sys_timer_ii. |
jshamlet |
1592d 10h |
/open8_urisc/trunk/VHDL/o8_sys_timer.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 |
1593d 13h |
/open8_urisc/trunk/VHDL/o8_sys_timer.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 |
1594d 06h |
/open8_urisc/trunk/VHDL/o8_sys_timer.vhd |
211 |
Ok, this time with feeling. Timer should now properly reset on interval update. |
jshamlet |
1600d 11h |
/open8_urisc/trunk/VHDL/o8_sys_timer.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 |
1600d 14h |
/open8_urisc/trunk/VHDL/o8_sys_timer.vhd |
194 |
Cleaned up licensing sections |
jshamlet |
1609d 08h |
/open8_urisc/trunk/VHDL/o8_sys_timer.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 |
1609d 09h |
/open8_urisc/trunk/VHDL/o8_sys_timer.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 |
1622d 07h |
/open8_urisc/trunk/VHDL/o8_sys_timer.vhd |
184 |
More file/entity renaming to match private versions. |
jshamlet |
1629d 09h |
/open8_urisc/trunk/VHDL/o8_sys_timer.vhd |
180 |
Added additional Open8 compatible modules |
jshamlet |
1634d 09h |
/open8_urisc/trunk/VHDL/o8_pit.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 |
3996d 02h |
/open8_urisc/trunk/VHDL/o8_pit.vhd |