59
Bit 1—Software Standby Output Port Enable (SSOE): Specifies whether the address bus and
bus control signals (
CS
0
to
CS
7
,
AS
,
RD
,
HWR
,
LWR
) are kept as outputs or fixed high, or
placed in the high-impedance state in software standby mode.
Bit 1
SSOE
Description
0
In software standby mode, the address bus and bus control signals are all high-
impedance
(Initial value)
1
In software standby mode, the address bus retains its output state and bus control
signals are fixed high
Bit 0—RAM Enable (RAME): Enables or disables the on-chip RAM. The RAME bit is
initialized by the rising edge of the
RES
signal. It is not initialized in software standby mode.
Bit 0
RAME
Description
0
On-chip RAM is disabled
1
On-chip RAM is enabled
(Initial value)
3.4
Operating Mode Descriptions
3.4.1
Mode 1
Ports 1, 2, and 5 function as address pins A
19
to A
0
, permitting access to a maximum 1-Mbyte
address space. The initial bus mode after a reset is 8 bits, with 8-bit access to all areas. If at least
one area is designated for 16-bit access in ABWCR, the bus mode switches to 16 bits.
3.4.2
Mode 2
Ports 1, 2, and 5 function as address pins A
19
to A
0
, permitting access to a maximum 1-Mbyte
address space. The initial bus mode after a reset is 16 bits, with 16-bit access to all areas. If all
areas are designated for 8-bit access in ABWCR, the bus mode switches to 8 bits.
3.4.3
Mode 3
Ports 1, 2, and 5 and part of port A function as address pins A
23
to A
0
, permitting access to a
maximum 16-Mbyte address space. The initial bus mode after a reset is 8 bits, with 8-bit access to
all areas. If at least one area is designated for 16-bit access in ABWCR, the bus mode switches to
16 bits. A
23
to A
21
are valid when 0 is written in bits 7 to 5 of the bus release control register
(BRCR). (In this mode A
20
is always used for address output.)
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