Fujitsu MB91401 bit1, bit0 WTH1, WTH0 Bus width setting bits, Operation mode, Prelminary, Remarks

Prelminary	MB91401
2004.11.12

[bit1, bit0] WTH1, WTH0 (Bus width setting bits)

These bits specify the bus width. The value of the bits is set in the DBW1 and DBW0 bits in ACR0 (CSO area). Set these bits to a value other than “11”.

WTH1	WTH0	Function	Remarks
0	0	8-bit bus width	External bus mode
0	1	16-bit bus width	External bus mode
1	0	32-bit bus width	External bus mode
1	1	Setting disabled

•Operation mode

In the operation mode, there are a bus mode and an access mode.

Bus mode

External ROM

bus

Access mode

32-bit bus width

16-bit bus width

8-bit bus width

Bus mode

In bus mode, the operations of internal ROM and the external access functions are controlled according to the mode setting pins (MD2 to MD0) and the values of mode data.

Although the FR71 architecture supports this bus mode, this macro cannot use the single-chip or internal ROM/ external bus mode but can use the external ROM/external bus mode only.

Access mode

Access mode indicates the mode that controls the external data bus width, and is specified by the WTH1/WTH0 bits, and the DBW1/DBW0 bits within ACR0 to ACR7 (Area Configuration Registers).

Bus mode

The FR family has three bus modes described below. Please refer to “■ MEMORY SPACE” for details.

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