HD6412373R RENESAS [Renesas Technology Corp], HD6412373R Datasheet - Page 319

• Manufacturer Part Number: HD6412373R
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2300 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Read after Write: If an external read occurs after an external write while the ICIS2 bit is set to 1
in BCR, an idle cycle is inserted at the start of the read cycle.
Figure 6.67 shows an example of the operation in this case. In this example, bus cycle A is a CPU
write cycle and bus cycle B is a read cycle from an external device. In (a), an idle cycle is not
inserted, and a collision occurs in bus cycle B between the CPU write data and read data from an
external device. In (b), an idle cycle is inserted, and a data collision is prevented.
Address bus
CS (area A)
CS (area B)
HWR, LWR
Data bus
RD
Figure 6.67 Example of Idle Cycle Operation (Read after Write)
φ
(a) No idle cycle insertion
T
(ICIS2 = 0)
1
Bus cycle A
Long output floating time
T
2
T
3
Bus cycle B
T
1
T
2
Data collision
Address bus
CS (area A)
CS (area B)
Data bus
HWR
RD
Rev.7.00 Mar. 18, 2009 page 251 of 1136
φ
T
(b) Idle cycle insertion
1
Bus cycle A
(ICIS2 = 1, initial value)
Section 6 Bus Controller (BSC)
T
2
T
3
Idle cycle
T
i
Bus cycle B
REJ09B0109-0700
T
1
T
2