M306V2 Mitsubishi, M306V2 Datasheet - Page 27

• Manufacturer Part Number: M306V2
• Description: SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER and ON-SCREEN DISPLAY CONTROLLER
• Manufacturer: Mitsubishi

Rev. 1.0
Table 2.4.1 Factors for switching bus settings
2.4.3 Bus Settings
Switching external address bus width
Switching external data bus width
Switching between separate and multiplex bus
The BYTE pin and bits 4 to 6 of the processor mode register 0 (address 0004
bus settings.
Table 2.4.1 shows the factors used to change the bus settings.
(1) Selecting external address bus width
(2) Selecting external data bus width
(3) Selecting separate/multiplex bus
The address bus width for external output in the 1M bytes of address space can be set to 16 bits (64K
bytes address space) or 20 bits (1M bytes address space). When bit 6 of the processor mode register
0 is set to “1”, the external address bus width is set to 16 bits, and P2 and P3 become part of the
address bus. P4
register 0 is set to “0”, the external address bus width is set to 20 bits, and P2, P3, and P4
become part of the address bus.
The external data bus width can be set to 8 or 16 bits. (Note, however, that only the separate bus can
be set.) When the BYTE pin is “L”, the bus width is set to 16 bits; when “H”, it is set to 8 bits. (The
internal bus width is permanently set to 16 bits.)
While operating, fix the BYTE pin either to “H” or to “L.”
The bus format can be set to multiplex or separate bus using bits 4 and 5 of the processor mode
register 0.
• Separate bus
In this mode, the data and address are input and output separately. The data bus can be set using the
BYTE pin to be 8 or 16 bits. When the BYTE pin is “H”, the data bus is set to 8 bits and P0 functions as
the data bus and P1 as a programmable I/O port. When the BYTE pin is “L”, the data bus is set to 16
bits and P0 and P1 are both used for the data bus.
When the separate bus is used for access, a software wait can be selected.
• Multiplex bus
In this mode, data and address I/O are time multiplexed. With an 8-bit data bus selected (BYTE pin =
“H”), the 8 bits from D
With a 16-bit data bus selected (BYTE pin = “L”), the 8 bits from D
D
mapped to the microcomputer’s even addresses (every 2nd address). To access these external de-
vices, access the even addresses as bytes.
The ALE signal latches the address. It is output from P5
Before using the multiplex bus for access, be sure to insert a software wait.
8
to D
15
are not multiplexed. In this case, the external devices connected to the multiplexed bus are
Bus setting
0
to P4
0
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
to D
3
can be used as programmable I/O ports. When bit 6 of processor mode
7
are multiplexed with A
Bit 6 of processor mode register 0
BYTE pin
Bits 4 and 5 of processor mode register 0
0
to A
6
.
7
.
and ON-SCREEN DISPLAY CONTROLLER
Switching factor
0
to D
MITSUBISHI MICROCOMPUTERS
7
M306V2ME-XXXFP
are multiplexed with A
16
) are used to change the
M306V2EEFP
0
1
to P4
to A
8
3
.
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