Atomic operations for MSP430 microcontrollers
Deprecated: This crate's functionality is a strict subset of portable-atomic
as of v0.3.16. Use portable-atomic v0.3.16 or greater going forward.
msp430-atomic uses inline asm to implement atomic opertions without
needing to disable interrupts. On MSP430, loads and stores of types
up to 16-bits are single instruction operations. These are atomic because
the current MSP430 instruction will run to completion before an interrupt
is serviced. Adding, subtracting, and logical operations on these types are
atomic in the same way, and msp430-atomic provides inline assembly for these
as well (add, sub, etc).
However, the standard APIs for atomic adds, subtracts, and logical operations
are also expected to return the old value before the operation (fetch_{add,sub,etc.}).
MSP430 has no single instructions to also return the old value while
simultaneously updating a memory location. Compare-And-Swap (CAS)
or Load-Link/Store Conditional
instructions can be used to implement these fetch_ instructions, but MSP430
has no such instructions either. Consequently, msp430-atomic does not provide
fetch_{add,sub,etc.}.
In contrast, portable-atomic provides load and stores using inline asm,
and implements fetch_{add,sub,etc.} by disabling interrupts. As of v0.3.16,
portable-atomic provides add, sub, etc. primitives which mirror the
public API of this crate (and don't disable interrupts).
Relationship to atomic-polyfill
atomic-polyfill uses the critical-section
crate to implement all atomic operations. For msp430, the critical-section
implementation usually means disabling interrupts. As of this writing
(11-06-2022), no optimizations that avoid disabling interrupts are provided
in atomic-polyfill.
Licensed under either of
-
Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
-
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.