M16CSLASH62 datasheet(47/615 Pages) RENESAS

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Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Bus Control

1-28

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

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

_______

In microprocessor mode, only CS0 outputs the chip select signal after the reset state has been can-

_______

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

and 1.9.2 show the external memory areas specified using the chip select signal.

Processor mode

Memory expansion mode

Chip select signal

CS0

CS1

CS2

CS3

3000016 to

CFFFF16

(640K bytes)

Microprocessor mode

2800016 to

2FFFF16

(32K bytes)

0800016 to

27FFF16

(128K bytes)

0400016 to

07FFF16

(16K bytes)

3000016 to

FFFFF16

(832K bytes)

Table 1.9.1. External areas specified by the chip select signals

(A product having an internal RAM equal to or less than 15K bytes and a ROM equal to or less than 192K bytes)(Note)

Note :Be sure to set bit 3 (PM13) of processor mode register 1 to “0”.

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