Hitachi SH7750 Hardware Manual page 392

• Idle Insertion between Accesses
Read
Preceding
CPU DMA
Cycle
Read
Write
DMA read
(memory →
device)
DMA write D
(device →
memory)
"DMA" in the table indicates DMA single-address transfer. DMA dual transfer is in accordance with
the CPU.
M, D: Idle wait always inserted by WCR1
(M(1): One cycle inserted in MPX access even if WCR1 is cleared to 0)
M: Idle cycles according to setting of AnIW2-AnIW0 (area 0 to area 6)
D: Idle cycles according to setting of DMAIW2-DMAIW0
Notes: When synchronous DRAM is used in RAS down mode, set bits DMAIW2-DMAIW0 to 000
and bits A3IW2-A3IW0 to 000.
*1 Inserted when device is switched
*2 On the MPX interface, a WCR1 idle wait may be inserted before an access (either read
or write) to the same area after a write access. The specific conditions for idle wait
insertion in accesses to the same area are shown below.
(a) Synchronous DRAM set to RAS down mode
(b) Synchronous DRAM accessed by on-chip DMAC
Apart from use under above conditions (a) and (b), an idle wait is also inserted between
an MPX interface write access and a following access to the same area. Even under
the above conditions, an idle wait may be inserted in a same-area access following an
interface write access, depending on the synchronous DRAM pipeline access situation.
An idle wait is not inserted when the WCR1 register setting is 0. The setting for the
number of idle state cycles inserted after a power-on reset is the default value of 15 (the
maximum value), so ensure that the optimum value is set.
Rev. 6.0, 07/02, page 342 of 986
Following Cycle
Same Area
Write
CPU DMA
M M
M M
1
D *
D D
Different Area
Read Write
CPU DMA CPU DMA
M M M
M M M
M M M
D D D
Same Different
Area Area
MPX MPX
Address Address
Output Output
M M (1) M (1)
2
*
M M
M — M (1)
D — D (1)