h8s-2635 Renesas Electronics Corporation., h8s-2635 Datasheet - Page 243

• Manufacturer Part Number: h8s-2635
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

(2) Write after Read
If an external write occurs after an external read while the ICIS0 bit in BCRH is set to 1, an idle
cycle is inserted at the start of the write cycle.
Figure 7-16 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.
+5
+5
*
*
*
4,
+5
B
+5
(a) Idle cycle not inserted
(ICIS1 = 0)
Figure 7-16 Example of Idle Cycle Operation (2)
4,
+5
+5
*
*
Rev. 6.00 Feb 22, 2005 page 183 of 1484
4,
B
(b) Idle cycle inserted
(Initial value ICIS1 = 1)
Section 7 Bus Controller
REJ09B0103-0600