M66222SP View Datasheet(PDF) - MITSUBISHI ELECTRIC

Part Name

Description

MFG CO.

M66222SP

128 × 8-BIT × 2 MAIL-BOX

MITSUBISHI ELECTRIC  

MITSUBISHI 〈DIGITAL ASSP〉

M66222SP/FP

128 × 8-BIT × 2 MAIL-BOX

FUNCTIONAL DESCRIPTION

The M66222 with independent and asynchronous accessibility from

two ports has the following four basic operations depending on an

address and mode set from both ports:

(1) A port .......... Write

B port .......... Write

(2) A port .......... Write

B port .......... Read

(3) A port .......... Read

B port .......... Write

(4) A port .......... Read

B port .......... Read

In this case, the same address is not selected when the same read/

write instruction is being executed at both ports as given in (1) and

(4). There is no concern about uncertainty of read/write data at an

active address. If one port operates in the write mode and the other

does in the read mode as given in (2) and (3), however, the same

address may be selected. In this case, data of the port operating in

the write mode is written. If the port in the read mode comes first,

read data of the first-in port becomes uncertain until write data of the

last-in port is determined (If the same address is selected, data of

the port operating in the write mode is written into memory. Therefore,

data of the port in the read mode may change from previously written

data to newly written ones during the same cycle) (See Fig 2).

Ex.) A port - address setting first-in read operation

B port - address setting last-in write operation

A port address

: When selecting the same address

B port address

WEB

B port I/O

(DIN)

Data B

(Data written from B port)

A port I/O

(DOUT)

Data A

(Data read to A port)

Data B

Fig 2 Example of Read Data Transition at Selection of Same Address

3

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