r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 332

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 6 Bus Controller (BSC)
6.12.3
Figure 6.96 shows the timing for transition to the bus released state.
Figure 6.97 shows the timing for transition to the bus released state with the synchronous DRAM
interface.
Rev. 1.00 Sep. 19, 2008 Page 302 of 1342
REJ09B0467-0100
Address bus
HWR, LWR
Data bus
BREQO
BREQ
BACK
RD
AS
[1] Low level of BREQ signal is sampled at rise of φ.
[2] Bus control signal returns to be high at end of external space access cycle.
[3] BACK signal is driven low, releasing bus to external bus master.
[4] BREQ signal state is also sampled in external bus released state.
[5] High level of BREQ signal is sampled.
[6] BACK signal is driven high, ending external bus release cycle.
[7] When there is external access or refresh request of internal bus master during external
[8] Normally BREQO signal goes high 1.5 states after rising edge of BACK signal.
φ
Transition Timing
At least one state from sampling of BREQ signal.
bus release while BREQOE bit is set to 1, BREQO signal goes low.
External space
access cycle
T
Figure 6.96 Bus Released State Transition Timing
1
[1]
T
2
[2]
[3]
[4]
[5]
External bus released state
High impedance
High impedance
High impedance
High impedance
High impedance
[6]
[7]
[8]
CPU
cycle