MB91401
33
[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”.
••••
Operation mode
In the operation mode, there are a bus mode and an access mode.
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.
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
Bus mode
Access mode
32-bit bus width
External ROM
bus
16-bit bus width
8-bit bus width
Summary of Contents for MB91401
Page 71: ...MB91401 71 MEMO ...
