42.3.2 BME decorated loads
The functions supported by the BME's decorated loads include two single-bit load-and-
{set, clear} operators plus unsigned bit field extracts.
For the two load-and-{set, clear} operations, BME converts a single decorated AHB load
transaction into a two-cycle atomic read-modify-write sequence, where the combined
read-modify operations are performed in the first AHB data phase, and then the write is
performed in the second AHB data phase as the original read data is returned to the
processor core. For an unsigned bit field extract, the decorated load transaction is stalled
for one cycle in the BME as the data field is extracted, then aligned and returned to the
processor in the second AHB data phase. This is the only decorated transaction that is not
an atomic read-modify-write, as it is a simple data read.
A generic timing diagram of a decorated load showing a peripheral load-and-set 1-bit
operation is shown as follows.
Chapter 42 Bit Manipulation Engine (BME)
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
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