M38005M2FS View Datasheet(PDF) - MITSUBISHI ELECTRIC

Part Name

Description

Manufacturer

M38005M2FS

8-BIT SINGLE-CHIP MICROCOMPUTER

MITSUBISHI ELECTRIC  

HARDWARE

FUNCTIONAL DESCRIPTION

Bus control with memory expansion

The 3800 group has a built-in ONW function to facilitate access to

external memory and I/O devices in memory expansion mode or

microprocessor mode.

If an “L” level signal is input to the ONW pin when the CPU is in a

read or write state, the corresponding read or write cycle is ex-

tended by one cycle of φ. During this extended period, the RD or

WR signal remains at “L”. This extension period is valid only for

writing to and reading from addresses 000016 to 000716 and

044016 to FFFF16 in microprocessor mode, 004016 to YYYY16 in

memory expansion mode, and only read and write cycles are ex-

tended.

Read cycle

Dummy cycle Write cycle Read cycle Dummy cycle

Write cycle

φ

AD15 to AD0

RD

WR

ONW

V

V

V

V : Period during which ONW input signal is received

During this period, the ONW signal must be fixed at either “H” or “L”. At all other times, the input level of the ONW

signal has no affect on operations.

The bus cycles is not extended for an address in the area 000816 to 043F16, regardless of whether the ONW signal

is received.

Fig. 30 ONW function timing

1-30

3800 GROUP USER’S MANUAL

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