| 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 |
1628d 08h |
/open8_urisc/trunk/VHDL/ |
| 243 |
Optimized code to prefer RAM vs register. |
jshamlet |
1635d 11h |
/open8_urisc/trunk/VHDL/ |
| 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 |
1635d 12h |
/open8_urisc/trunk/VHDL/ |
| 241 |
Added an Open8 compatible 7-segment display/decoder and uploaded local/private documentation. |
jshamlet |
1640d 07h |
/open8_urisc/trunk/VHDL/ |
| 240 |
Simplified the vector tx/rx system to a single line. An idle detector replaces the attn_req signal. |
jshamlet |
1642d 11h |
/open8_urisc/trunk/VHDL/ |
| 231 |
Updated sample projects and added elapsed time capture (chronometer) module |
jshamlet |
1657d 15h |
/open8_urisc/trunk/VHDL/ |
| 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 |
1661d 12h |
/open8_urisc/trunk/VHDL/ |
| 228 |
Added an initialization constant for the OPEN8_BUS_TYPE record. |
jshamlet |
1662d 02h |
/open8_urisc/trunk/VHDL/ |
| 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 |
1662d 09h |
/open8_urisc/trunk/VHDL/ |
| 226 |
Forgot the updated package file... |
jshamlet |
1662d 13h |
/open8_urisc/trunk/VHDL/ |
| 225 |
Added Halt_Ack to go with Halt_Req. |
jshamlet |
1662d 13h |
/open8_urisc/trunk/VHDL/ |
| 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 |
1662d 15h |
/open8_urisc/trunk/VHDL/ |
| 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 |
1663d 08h |
/open8_urisc/trunk/VHDL/ |
| 222 |
Created a modified version of the epoch timer with a 32-bit, 1-uS resolution timer/comparator. |
jshamlet |
1663d 14h |
/open8_urisc/trunk/VHDL/ |
| 221 |
o8_vdsm8.vhd now has a default value assigned at compile time, o8_register.vhd was cleaned up some more. |
jshamlet |
1664d 08h |
/open8_urisc/trunk/VHDL/ |
| 220 |
More revision sections added |
jshamlet |
1664d 08h |
/open8_urisc/trunk/VHDL/ |
| 219 |
Added revision block and corrected creation date. |
jshamlet |
1664d 09h |
/open8_urisc/trunk/VHDL/ |
| 218 |
Revision sections added,
vdsm8.vhd added. |
jshamlet |
1664d 09h |
/open8_urisc/trunk/VHDL/ |
| 217 |
Broke out the vdsm8 as a separate entity, since it is used in several places,
Even MORE code cleanup. |
jshamlet |
1664d 09h |
/open8_urisc/trunk/VHDL/ |
| 216 |
Fixed missing parenthesis |
jshamlet |
1664d 11h |
/open8_urisc/trunk/VHDL/ |
