r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 328

• Manufacturer Part Number: r4f2426
• 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.
Rev. 1.00 Sep. 19, 2008 Page 300 of 1270
REJ09B0466-0100
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