Reworked PUSH into push8.imm and push8.? (for future implementation of other non-immediate push8s). Implemented push16.imm and push16.? including their unit test and register transfer diagram. Started working on push16.pc, but ran into an issue where PC is incremented within FETCH, […]
Finished implementing PUSH, including the unit test for it. All seems to be working now, and I fixed a lot of bugs related to RAM while working on this, as this is the first use of RAM in the system. […]
Started working on the unit test for PUSH, found that I hadn’t ever implemented the SP register despite it being the design. Did so, and then did a bunch of troubleshooting related to the new register. At this point tests […]
Added a first stab at some microcode for PUSH, which is a prerequisite for being able to implement CALL and RETURN. Next step will be to write a useful unit test for it so we can confirm it’s working properly […]
Figured out and diagrammed the initials parts of the logic for handling interrupts. Next step is to implement CALL/RETURN, which will be needed to integrate the design into the system.
Added supervisor/user mode support and a test for it, everything works as intended. Still need to write the unit test for branch-if-CO.
Added conditional branch support and a test for it. Currently only have a test for the branch-if-Z path, not the branch-if-CO path. Next step will be to add a unit test for branch-if-CO, then probably work on fault/trap/interrupt support.
Added support for ALU status bits Z (last operation result was zero) and OC (overflow/carry out) and tests for them. Also added add8.ab which adds lower bytes of registers A and B. Next step will be to add conditional branch […]
Wrote a new unit test system, and implemented tests for all current instructions. Next step will probably be to look at implementation of ALU status bits, so we can do branching in the future.
Implemented ldi8.flags so that paging can be turned on. Fixed a couple bugs in the system, and now paging works! Also while working on this, I renamed PID to PTB (page table block) as one PID could potentially use more […]