134
Area 6: Area 6 is an area with address bits A26–A24 set to 110 and an address range of
H'6000000–H'6FFFFFF and H'E000000–H'EFFFFFF. Figure 8.9 shows a memory map of area 6.
In area 6, a space for which address bit A27 is 0 is allocated to address/data multiplexed I/O space
when the multiplexed I/O enable bit (IOE) of the bus control register (BCR) is 1, and to external
memory space when the IOE bit is 0. When A27 is 1, it is always external memory space.
The multiplexed I/O space is a type of external memory space but the address and data are
multiplexed and output from AD15–AD0 or AD7–AD0. The bus width is 8 bits when the A14 bit
is 0 and 16 bits when the A14 bit is 1. The A23 and A22 bits are not output and the shadow is in 4-
Mbyte units. When multiplexed I/O space is accessed, the
CS6
signal is valid.
In external memory space, the bus width is 8 bits when both the A27 and A14 bits are 0 and 16
bits when the A27 bit is 0 and the A14 bit is 1. When the A27 bit is 1, it is always a 16-bit space.
The A23 and A22 bits are not output and the shadow is in 4-Mbyte units. When external memory
is accessed, the
CS6
signal is valid. The external memory space has a long wait function so
between 1 and 4 states can be selected for the number of long waits inserted into the bus cycle
using the area 6 long wait insertion bits (A6LW1 and A6LW0) in WCR3.
H'E000000
H'E400000
H'E800000
H'EC00000
H'E3FFFFF
H'E7FFFFF
H'EBFFFFF
H'EFFFFFF
Shadow
Shadow
Shadow
Shadow
External
memory
space
(4 Mbytes)
H'6000000
H'6400000
H'6800000
H'6C00000
H'63FFFFF
H'67FFFFF
H'6BFFFFF
H'6FFFFFF
Shadow
Shadow
Shadow
Shadow
Multiplexed
I/O space
or external
memory
space
(4 Mbytes)
Logical address
space
Logical address
space
8 or 16-bit
space
16-bit space
Actual
space
Actual
space
• IOE = 1:
address/data
multiplexed I/O
space;
IOE = 0: external
memory space
• A14 = 0: 8-bit space
A14 = 1: 16-bit space
• Valid addresses
A21–A0 (A23 and
A22 not output)
•
CS6
valid
• Long wait function
• Valid
addresses
A21–A0 (A23
and A22 not
output)
•
CS6
valid
• Long wait
function
Figure 8.9 Memory Map of Area 6
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