SPRUJ79 November 2024 F29H850TU , F29H859TU-Q1
The ROM memory controller has a 256-bit dataline buffer. The latest CPU data access from ROM is stored in the dataline buffer. ECC bits are stored with data. Program accesses from the CPU do not affect the dataline buffer. During a simultaneous data read access from bus 1 and bus 2, if the address of the accesses is within the 256-bit aligned address then only one access is issued to ROM. The second access is served from the same data. Debug read access is not buffered in the dataline buffer.
The dataline buffer is flushed when the CPU enters a fault state. The test mode does not affect the dataline buffer operation since ROM is read-only. Depending on the test mode setting, either data or ECC bits are returned.