M16CSLASH62 datasheet(41/621 Pages) RENESAS

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Mitsubishi microcomputers

M16C / 62 Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Memory Space Expansion Functions

The data bank register is made up of the bank selection bits (bits 5 through 3) and the offset bit (bit 2). The

bank selection bits are used to set a bank number for accessing data lying between 4000016 and

BFFFF16. Assigning 1 to the offset bit provides the means to set offsets covering 4000016.

Figure 1.8.5 shows the memory location and chip select areas in expansion mode 2.

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The area relevant to CS0 ranges from 4000016 through FFFFF16. As for the area from 4000016 through

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BFFFF16, the bank number set by use of the bank selection bits are output from the output terminals CS3

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- CS1 only in accessing data. In fetching a program, bank 7 (1112) is output from CS3 - CS1. As for the

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area from C000016 through FFFFF16, bank 7 (1112) is output from CS3 - CS1 without regard to accessing

data or to fetching a program.

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In accessing an area irrelevant to CS0, a chip select signal CS3 (400016 - 7FFF16), CS2 (800016 -

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27FFF16), and CS1 (2800016 - 3FFFF16) is output depending on the address as in the past.

Figure 1.8.6 shows an example of connecting the MCU with a 4-M byte ROM and to a 128-K byte SRAM.

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Connect the chip select of 4-M byte ROM with CS0. Connect M16C’s CS3, CS2, and CS1 with address

inputs AD21, AD20, and AD19 respectively. Connect M16C’s output A19 with address input AD18. Fig-

ure 1.8.7 shows the relationship between addresses of the 4-M byte ROM and those of M16C.

An example of connecting the MCU with

external memories in expansion mode 2

(M30622MC, Microprocessor mode)

D0 to D7

A0 to A16

A17

CS1

CS2

CS3

CS0

A19

DQ0 to DQ7

AD0 to AD16

AD17

AD18

AD19

DQ0 to DQ7

AD0 to AD16

AD20

AD21

Note: If only one chip select terminal (S1 or S2) is present,

decoding by use of an external circuit is required.

In this mode, memory is

banked every 512 K bytes,

so that data access in differ-

ent banks requires switching

over banks. However, data

on bank boundaries when

offset bit = 0 can be ac-

cessed successively by set-

ting the offset bit to 1, be-

cause in which case the

memory address is offset by

4000016. For example, two

bytes of data located at ad-

dresses 0FFFFF 16 and

10000016 of 4-Mbyte ROM

can be accessed succes-

sively without having to

change the bank bit by set-

ting the offset bit to 1 and

then accessing addresses

07FFFF16 and 80000016.

On the other hand, the

SRAM’s chip select assumes

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that CS0=1 (not selected)

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and CS2=0 (selected), so

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connect CS0 with S2 and

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____

CS2 with S1. If the SRAM

doesn’t have a bipolar chip

select input terminal, decode

_______

CS0 and CS2 externally.

Figure 1.8.6. An example of connecting the MCU with external

memories in expansion mode 2

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