W78958B

- 4 -

PIN DESCRIPTION

ENSTD Enable Standard Type, Input, Active Low

TYPE

MODE

DESCRIPTION

Advanced

-

Default status is pulled high by internal pull-up resistor.

Standard

-

A low on this pin enables the standard type.

Note: "-" in "Mode" column means that the function description is valid in both modes, normal and emulation.

EA External Address, Input

TYPE

MODE

DESCRIPTION

Advanced

-

Functions same as in W78C438.

Standard

-

Functions same as in W78C51, W78C52, W78C154* or W78C58.

PSEN

TYPE

MODE

DESCRIPTION

Advanced

Normal

Functions same as in W78C438.

Emulation

In high impedance state.

Standard

Normal

Pins ROMS1 and ROMS0 determine the function of PSEN. For

details, see Table D1 below.

Emulation

In high impedance state.

ROMS1

ROMS0

FUNCTION of PSEN, PORT 0, AND PORT 2

0

0

Same as in the W78C51 (verify 4K ROM).

0

1

Same as in the W78C52 (verify 8K ROM).

1

0

Same as in the W78C154* (verify 16K ROM).

1

1

Same as in the W78C58 (verify 32K ROM).

Table D1.

ALE

TYPE

MODE

DESCRIPTION

Advanced

Normal

Functions same as in W78C32.

Emulation

In high impedance state.

Standard

Normal

Functions same as in W78C52.

Emulation

In high impedance state.