MB91155 datasheet(24/105 Pages) FUJITSU

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MB91F155A/MB91155/MB91154

s SETTING MODE

Mode Pins

As shown in Table 1 three pins, MD2, 1, and 0 are used to indicate an operation.

Table 1 Mode pins and set modes

Mode Data

The data which the CPU writes to “0000 07FFH” after reset is called mode data.

It is the mode register (MODR) that exists at “0000 07FFH.” Once a mode is set in this register, operations will

take place in that mode. The mode register can be written only once after reset.

The mode specified in the register is enabled immediately after it is written.

[bits 7 and 6] : M1, M0

These are bus mode setting bits. Specify the bus mode to be set to after writing to the mode register.

[bits 5 to 0] :

∗

These bits are reserved for the system.

Mode pin

Mode name

Reset vector

access area

External data

bus width

MD2

MD1

MD0

External vector mode 0

External

8 bits

External ROM bus mode

External vector mode 1

External

16 bits

External vector mode 2

External

32 bits

Not available on this

product type

External vector mode

Internal

(Mode register)

Single-chip mode





Not available

Function

Remarks

Single-chip mode

Internal ROM-external bus mode

External ROM-external bus mode



Setting not allowed

“0” should be written to these bits at all times.

MODR

Initial value Access

Address : 0000 07FFH

XXXXXXXX

W : Write only, X : Undefined

Bus mode setting bits

∗∗∗∗

∗

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