M306H2MC-XXXFP Datasheet, PDF (26/210 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

MITSUBISHI MICROCOMPUTERS
M306H2MC-XXXFP
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
with DATA ACQUISITION CONTROLLER
2.4.2 Bus Control
The following explains the signals required for accessing external devices and software waits.
The signals required for accessing the external devices are valid when the processor mode is set to
memory expansion mode and microprocessor mode. The software waits are valid in all processor modes.
(1) Address bus/data bus
The address bus consists of the 20 pins A0 to A19 for accessing the 1M bytes of address space.
The data bus consists of the pins for data I/O. When the BYTE pin is “H”, the 8 ports D0 to D7 function
as the data bus. When BYTE is “L”, the 16 ports D0 to D15 function as the data bus.
When a change is made from single-chip mode to memory expansion mode, the value of the address
bus is undefined until external memory is accessed.
(2) Chip select signal
The chip select signal is output using the same pins asP4 4 to P47. Bits 0 to 3 of the chip select
control register (address 000816) set each pin to function as a port or to output the chip select signal.
The chip select control register is valid in memory expansion mode and microprocessor mode. IN
single-chip mode,P4 4 to P47 function as programmable I/O ports regardless of the value in the chip
select control register.
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In microprocessor mode, only CS0 outputs the chip select signal after the reset state has been
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cancelled. CS1 to CS3 function as input ports. Figure 2.4.3 shows the chip select control register.
The chip select signal can be used to split the external area. Tables 2.4.3 show the external memory
areas specified using the chip select signal.
Table 2.4.3 External areas specified by the chip select signals
Processor mode
CS0
Chip select signal
CS1
CS2
CS3
Memory expansion
mode
Microprocessor mode
3000016 to
CFFFF16
(640K bytes)
3000016 to
FFFFF16
(832K bytes)
2800016 to
2FFFF16
(32K bytes)
0800016 to
27FFF16
(128K bytes)
0400016 to
07FFF16
(16K bytes)
Chip select control register
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
CSR
Address
000816
When reset
0116
Bit symbol
CS0
CS1
CS2
CS3
CS0W
CS2W
CS2W
CS3W
Bit name
CS0 output enable bit
CS1 output enable bit
CS2 output enable bit
CS3 output enable bit
CS0 wait bit
CS1 wait bit
CS2 wait bit
CS3 wait bit
Function
0 : Chip select output disabled
(Normal port pin)
1 : Chip select output enabled
RW
0 : Wait state inserted
1 : No wait state
Figure 2.4.3 Chip select control register
Rev. 1.0
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