h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 209

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

6.5.3
As with the basic bus interface, either program wait insertion or pin wait insertion using the WAIT
pin can be used in the initial cycle (full access) of the burst ROM interface. See section 6.4.5, Wait
Control.
Wait states cannot be inserted in a burst cycle.
6.6
6.6.1
When the H8S/2138 Group or H8S/2134 Group chip accesses external space, it can insert a 1-state
idle cycle (T
inserting an idle cycle it is possible, for example, to avoid data collisions between ROM, with a
long output floating time, and high-speed memory, I/O interfaces, and so on.
If an external write occurs after an external read while the ICIS0 bit in BCR is set to 1, an idle
cycle is inserted at the start of the write cycle. This is enabled in advanced mode and normal
mode.
Figure 6.9 shows an example of the operation in this case. In this example, bus cycle A is a read
cycle from ROM with a long output floating time, and bus cycle B is a CPU write cycle. In (a), an
idle cycle is not inserted, and a collision occurs in cycle B between the read data from ROM and
the CPU write data. In (b), an idle cycle is inserted, and a data collision is prevented.
Idle Cycle
Operation
Wait Control
I
) between bus cycles when a write cycle occurs immediately after a read cycle. By
Rev. 4.00 Jun 06, 2006 page 155 of 1004
Section 6 Bus Controller
REJ09B0301-0400