Rev.6.00 Oct.28.2004 page 115
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REJ09B0138-0600H
Bit 6—BREQO Pin Enable (BREQOE): Outputs a signal that requests the external bus master to drop the bus request
signal (
BREQ
) in the external bus release state, when an internal bus master performs an external space access, or when a
refresh request is generated.
Bit 6
BREQOE
Description
0
BREQO
output disabled.
BREQO
can be used as I/O port.
(Initial value)
1
BREQO
output enabled.
Bit 5—External Address Enable (EAE): Selects whether addresses H'010000 to H'01FFFF*
2
are to be internal addresses
or external addresses.
Bit 5
EAE
Description
0
Addresses H'010000 to H'01FFFF
*
2
are in on-chip ROM
1
Addresses H'010000 to H'01FFFF
*
2
are external addresses (external expansion mode)
or a reserved area
*
1
(single-chip mode)
(Initial value)
Notes: 1. Reserved areas should not be accessed.
2. Addresses H'010000 to H'01FFFF are in the H8S/2357. Addresses H'010000 to H'03FFFF are in the H8S/2398.
Bit 4—LCAS Select (LCASS): Write 0 to this bit when using the DRAM interface.
LCAS
pin used for 2-CAS type DRAM interface
LCAS
signal.
BREQO
output and
WAIT
input cannot be used when
LCAS
signal is used.
Bit 3—DACK Timing Select (DDS): Selects the DMAC single address transfer bus timing for the DRAM interface.
Bit 3
DDS
Description
0
When DMAC single address transfer is performed in DRAM space, full access is
always executed
DACK
signal goes low from T
r
or T
1
cycle
1
Burst access is possible when DMAC single address transfer is performed in DRAM
space
DACK
signal goes low from T
c1
or T
2
cycle
(Initial value)
Bit 2—Reserved: Only 1 should be written to this bit.
Bit 1—Write Data Buffer Enable (WDBE): Selects whether or not the write buffer function is used for an external write
cycle or DMAC single address cycle.
Bit 1
WDBE
Description
0
Write data buffer function not used
(Initial value)
1
Write data buffer function used
Содержание ZTAT H8S/2357F
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