Datasheet

Table Of Contents
Section 6 Bus Controller
Page 146 of 846 REJ09B0140-0900 Rev. 9.00
Sep 16, 2010
H8S/2215 Group
Figure 6.25 shows the timing for transition to the bus-released state.
CPU
cycle
Address
Minimum
1 state
T
0
T
1
T
2
HWR, LWR
BREQ
BACK
High impedance
High impedance
AS
CSn
High impedance
High impedance
High impedance
RD
High impedance
Data bus
Address bus
φ
[1] [2] [3] [4] [5]
[1] Low level of BREQ pin is sampled at rise of T
2
state.
[2] BACK pin is driven low at end of CPU read cycle, releasing bus to external bus
master.
[3] BREQ pin state is still sampled in external bus released state.
[4] High level of BREQ pin is sampled.
[5] BACK pin is driven high, ending bus release cycle.
CPU cycle External bus released state
Note : n = 0 to 7
Figure 6.25 Bus-Released State Transition Timing
6.9.1 Notes on Bus Release
The external bus release function halts when a transition is made to sleep mode while MSTPCR is
set to H'FFFFFF. To use the external bus release function in sleep mode, do not set MSTPCR to
H'FFFFFF.