
GR716-DS-UM, May 2019, Version 1.29
159
www.cobham.com/gaisler
GR716
tection unit, see chapter TBD. A write to a protected area without write permission to will result in a
AMBA error and the write request to the memory will be ignored.
Figure 17 shows a block diagram of the internals of the controller.
Operation
The EDAC checksum is always updated for write operations, but only checked during reads when
enabled by the LRAMCFG.EN configuration field. When correctable error is detected a counter
LRAMCFG.ECNT is incremented and can be used to monitor the error rate.
When a uncorrectable error is detected the read operation will complete with an error response.
20.1.1 AHB interface
For single read or the first beat in a read burst the access is performed with 2 wait-states. For the con-
tinuing read burst no wait-states are added to the access. Sub-word writes has the same bus timing as
single read and the access is performed with 2 wait-states. Sub-word writes are performed as an read-
modify-write operation by the memory controller to be able to correctly update the checksum. For
word write no wait-states are added. The access on the AHB port could be stalled due to scrub opera-
tions or when a write conflict is detected between the AHB port and the CPU port. When the CPU
port performs a read to a specific address, a write on the AHB port to the same address is stalled until
the CPU read has completed. This feature is enabled by the LRAMCFG.PC configuration field.
Correctable errors are automatically corrected and not visible on the AHB bus (the auto-correction
feature can be disabled by the LRAMCFG.ACOR configuration field). When an uncorrectable error is
detected the access will terminate with an AMBA ERROR response.
When a write-protected area (defined by the AMBA protection unit) is written the access will be ter-
minated with a AMBA ERROR response.
20.1.2 Processor interface
The CPU port is designed to allow word reads and writes with no stalling. Sub-word writes is
assumed to be performed as a read-modify-write by the CPU. This port is not affected by the scrub-
bing operations.
The atomic operations OR, AND, XOR, Set&Clear is mapped at an offset described in the Atomic
operation section and is only supported for the data memory.
Correctable errors are automatically corrected and not visible for the CPU (the auto-correction feature
can be disabled by the LRAMCFG.ACOR configuration field). When an uncorrectable error is
detected the access will terminate with a data_access/store_exception.
Figure 17.
Block diagram
Processor
Interface
AHB Slave
Interface
LEON3FT
AHB bus
Encoder /
Decoder
Encoder /
Decoder
Scrubber
Config
LRAM_CPU_AHB
(Auto-correct)
Interface
APB bus
SYNCRAM
DP