M32CSLASH86 datasheet(77/505 Pages) RENESAS

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8. Bus

)

(

8. Bus

In memory expansion mode or microprocessor mode, some pins function as bus control pins to control the

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_________ ______

_________ _______

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address bus and data bus. A0 to A22, A23, D0 to D15, CS0 to CS3, WRL/WR, WRH/BHE, RD, BCLK/ALE,

_________

_______

HLDA/ALE, HOLD, ALE, RDY are used as bus control pins.

Bus control pins in M32C/86T cannot be used.

8.1 Bus Settings

The BYTE pin, the DS register, the PM05 and PM04 bits in the PM0 register and the PM11 and PM10 bits

in the PM1 register determine bus settings.

Table 8.1 lists how to change bus settings. Figure 8.1 shows the DS register.

Table 8.1 Bus Settings

Bus Setting

Changed By

Selecting External Address Bus Width

DS register

Setting Bus Width after Reset

BYTE pin (external space 3 only)

Selecting Between Separate Bus or Multiplexed Bus

PM05 and PM04 bits in PM0 register

Number of Chip-Select

PM11 and PM10 bits in PM1 register

Figure 8.1 DS Register

Symbol

Address

After Reset

000B16

XXXX 10002 (BYTE pin = "L")

XXXX 00002 (BYTE pin = "H")

External Data Bus Width Control Register

DS0

DS1

DS2

DS3

(b7 - b4)

0 : 8 bits wide

1 : 16 bits wide

0 : 8 bits wide

1 : 16 bits wide

0 : 8 bits wide

1 : 16 bits wide

0 : 8 bits wide

1 : 16 bits wide

Bit Name

Function

Bit

Symbol

Nothing is assigned. When write, set to "0".

When read, its content is indeterminate.

External Space 0 Data

Bus Width Select Bit

External Space 1 Data

Bus Width Select Bit

External Space 2 Data

Bus Width Select Bit

External Space 3 Data

Bus Width Select Bit(1)

NOTES:

1. The DS register in M32C/86T cannot be used.

NOTE

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