HD6417660 RENESAS [Renesas Technology Corp], HD6417660 Datasheet - Page 218

• Manufacturer Part Number: HD6417660
• Description: Renesas 32-Bit RISC Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

5.2.2
Cache Control Register 2 (CCR2)
The CCR2 register controls the cache locking mechanism in DSP mode only. The CPU enters
DSP mode when the DSP bit (bit 12) in the status register (SR) is set to 1. The cache locking
mechanism is disabled in non-DSP mode (DSP bit = 0).
When a prefetch instruction (PREF@Rn) is issued in DSP mode and a cache miss occurs, the line
of data pointed to by Rn will be loaded into the cache, according to the setting of bits 9 and 8
(W3LOAD, W3LOCK) and bits 1 and 0 (W2LOAD, W2LOCK in CCR2).
Table 5.2 shows the relationship between the settings of bits and the way that is to be replaced
when the cache is missed by a prefetch instruction.
On the other hand, when the cache is hit by a prefetch instruction, new data is not loaded into the
cache and the valid entry is held. For example, a prefetch instruction is issued while bits
W3LOAD and W3LOCK are set to 1 and the line of data to which Rn points is already in way 0,
the cache is hit and new data is not loaded into way 3.
In DSP mode, bits W3LOCK and W2LOCK restrict the way that is to be replaced, when
instructions other than the prefetch instruction are issued. Table 5.3 shows the relationship
between the settings of bits in CCR2 and the way that is to be replaced when the cache is missed
by instructions other than the prefetch instruction.
Programs that change the contents of the CCR2 register should be placed in address space that is
not cached.
Rev. 1.00, 02/04, page 180 of 804