| Rev |
Log message |
Author |
Age |
Path |
| 253 |
Fixed spelling error in comment |
jshamlet |
1742d 10h |
/open8_urisc/ |
| 252 |
(This time the CPU model was included...)
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 |
1742d 10h |
/open8_urisc/ |
| 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 |
1742d 10h |
/open8_urisc/ |
| 250 |
Removed monitor RAM from SDLC model, as it is now proven to work. |
jshamlet |
1746d 18h |
/open8_urisc/ |
| 249 |
Added a 32-bit wide register and split the status_led core from o8_status_led.vhd, allowing it to be used as a subcomponent elsewhere. |
jshamlet |
1758d 10h |
/open8_urisc/ |
| 248 |
Removed Default_Int_Flag generic from CPU, as it is duplicated by Supervisor_Mode. |
jshamlet |
1758d 18h |
/open8_urisc/ |
| 247 |
Fixed problem where parallel interface was always forcing the data registers due to bad alias. |
jshamlet |
1759d 11h |
/open8_urisc/ |
| 246 |
The system timer module now allows for an optional millisecond resolution (settable through a generic). This prescalar enable permits the timer to operate from 1 to 256 mS, which is useful for a variety of tasks, such as serial timeouts and watchdog timers. The enable is not software settable, as this would complicate the register interface and isn't generally useful in an HDL based SOC design.
The vector interface now has a parallel interface that runs beside the serial interface, and is useful for connecting to DIO cards or other parallel interfaces. |
jshamlet |
1759d 16h |
/open8_urisc/ |
| 245 |
Modified the CPU's Supervisor_Mode to also protect SMSK and RSP instructions,
Added an external interrupt manager, o8_int_mgr.vhd. |
jshamlet |
1761d 15h |
/open8_urisc/ |
| 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 |
1762d 11h |
/open8_urisc/ |
| 243 |
Optimized code to prefer RAM vs register. |
jshamlet |
1769d 15h |
/open8_urisc/ |
| 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 |
1769d 15h |
/open8_urisc/ |
| 241 |
Added an Open8 compatible 7-segment display/decoder and uploaded local/private documentation. |
jshamlet |
1774d 10h |
/open8_urisc/ |
| 240 |
Simplified the vector tx/rx system to a single line. An idle detector replaces the attn_req signal. |
jshamlet |
1776d 14h |
/open8_urisc/ |
| 239 |
More cleanup and notation of board to board I/O |
jshamlet |
1776d 19h |
/open8_urisc/ |
| 238 |
Removed extraneous reference to Ints.VEC_Flag from task.s, since it is supposed to be in the init function in test_fn.s. |
jshamlet |
1777d 14h |
/open8_urisc/ |
| 237 |
Found some errors in the comments and cleaned up unnecessary library references. |
jshamlet |
1777d 17h |
/open8_urisc/ |
| 236 |
More software cleanup for the Open8_II project |
jshamlet |
1777d 18h |
/open8_urisc/ |
| 235 |
Ok, this time with feeling. |
jshamlet |
1782d 12h |
/open8_urisc/ |
| 234 |
Forgot to add documentation |
jshamlet |
1782d 14h |
/open8_urisc/ |
