mirror of
https://github.com/transistorfet/moa.git
synced 2024-11-24 23:32:46 +00:00
Fixed some grammatical mistakes
This commit is contained in:
parent
ea2fc95905
commit
2cc7db8bf5
@ -39,8 +39,8 @@ for the 68000, and expand the implementation from there. Once we've created a w
|
||||
passage of time for the CPUs and I/O devices, we'll implement a simple serial port controller which
|
||||
will act as our primary I/O device. From there we'll make all of our simulated devices, represented
|
||||
as `struct` objects in Rust, look the same so that we can treat them the same, regardless of what
|
||||
they represent internally. We'll then be able to package them up into single working system and set
|
||||
them in motion to run the Computie software from binaries images.
|
||||
they represent internally. We'll then be able to package them up into a single working system and
|
||||
set them in motion to run the Computie software from binary images.
|
||||
|
||||
* [The Computer](#the-computer)
|
||||
* [The 68000](#the-68000)
|
||||
@ -66,7 +66,7 @@ and an MC68681 dual serial port controller, which handles most of the I/O. (The
|
||||
minor fixes which won't affect us here. I'll mostly be referring to the common aspects of both
|
||||
processors). One of the serial connections is used as a TTY to interact with either the unix-like
|
||||
Computie OS, or the monitor software that's normally stored in the flash chip. It also supports a
|
||||
CompactFlash card and SLIP connection over the other serial port for internet access, but we wont
|
||||
CompactFlash card and SLIP connection over the other serial port for internet access, but we won't
|
||||
cover those here. In order to get a working emulator, we'll focus on just the CPU, memory, and
|
||||
MC68681 controller.
|
||||
|
||||
@ -112,7 +112,7 @@ first address contains the value to be loaded into the Supervisor stack register
|
||||
remaining addresses are the value loaded into the program counter when a given exception occurs.
|
||||
This table cannot be relocated on the 68000, but it can be changed after reset on the 68010.
|
||||
Computie uses the 68010 for this exact feature, so that the OS can put the vector table in RAM, but
|
||||
the monitor software doesn't use interrupts. We wont cover interrupts here so this feature isn't
|
||||
the monitor software doesn't use interrupts. We won't cover interrupts here so this feature isn't
|
||||
needed for now and we can focus only on emulating the 68000. As for the vector table, we just need
|
||||
to simulate how the processor starts up on power on or after a reset, in which case the vector table
|
||||
is always at address 0, and the first two long words are the stack pointer and initial program
|
||||
@ -160,7 +160,7 @@ I went through a few different iterations of this, especially for the `.read()`
|
||||
returned an iterator over the data starting at the address given, which works well for simulated
|
||||
memory, but reading from an I/O device could return data that is unique to when it was read. For
|
||||
example, when reading the next byte of data from a serial port, the data will be removed from the
|
||||
device's internal FIFO and returned, and since at that point it wont be stored anywhere, we can't
|
||||
device's internal FIFO and returned, and since at that point it won't be stored anywhere, we can't
|
||||
have a reference to it. We need the data (of variable length) to be owned by the caller when the
|
||||
method returns, and passing in a reference to a mutable array to hold that data is a simple way to
|
||||
do that.
|
||||
@ -202,7 +202,7 @@ pub fn write_beu16(data: &mut [u8], value: u16) -> &mut [u8] {
|
||||
|
||||
Now for some simulated ram that implements our trait. (I'm leaving out the `.new()` methods for
|
||||
most of the code snippets because they are pretty straight-forward, but you can assume they exist,
|
||||
and take the their field values as arguments, or set their fields to 0).
|
||||
and take their field values as arguments, or set their fields to 0).
|
||||
|
||||
```rust
|
||||
pub struct MemoryBlock {
|
||||
@ -514,7 +514,7 @@ that our `Clock` value will be the number of nanoseconds from the start of the s
|
||||
a `u64` here so that we can keep track of simulation time in nanoseconds for approximately 584 which
|
||||
*should* be enough. Keeping track of the time will allow us to later limit how much time passes
|
||||
(either speeding up or slowing down the execution relative to real-time). With this, we can get a
|
||||
somewhat accurate count when simulating the timer in the serial controller chip. That said, we wont
|
||||
somewhat accurate count when simulating the timer in the serial controller chip. That said, we won't
|
||||
worry about simulating CPU execution times, which varies quite a bit based on each instruction and
|
||||
it's operands, so can add a lot of complexity.
|
||||
|
||||
@ -635,7 +635,7 @@ the serial port controller (`MC68681`). The CPU implements the `Steppable` trai
|
||||
implements the `Addressable` trait, and the controller implements both. That last one is a problem
|
||||
because we can't have two mutable references to both the `Addressable` and `Steppable` trait objects
|
||||
of the controller at the same time, and rust doesn't yet support trait objects implementing multiple
|
||||
traits under these conditions. Generics wont work either because we need to store the
|
||||
traits under these conditions. Generics won't work either because we need to store the
|
||||
`Addressable`s in some kind of list, and items in a list must have the same type, so we need some
|
||||
other way of getting a reference to one of the trait objects only when we need to use it. If we
|
||||
weren't so adamant about making this flexible and configurable, we could possibly keep this simpler,
|
||||
|
Loading…
Reference in New Issue
Block a user