M16C30_02 Datasheet, PDF (27/178 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Bus Control
Mitsubishi microcomputers
M16C / 30 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
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 as P44 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, P44 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 can-
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celled. CS1 to CS3 function as input ports. Figure 1.9.1 shows the chip select control register.
The chip select signal can be used to split the external area into as many as four blocks. Tables 1.9.1
shows the external memory areas specified using the chip select signal.
Table 1.9.1. External areas specified by the chip select signals
Processor mode
Chip select signal
CS0
CS1
CS2
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)
CS3
0400016 to
07FFF16
(16K bytes)
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