M27C400 datasheet(2/14 Pages) STMICROELECTRONICS

2 / 14 page

M27C400

2/14

Figure 2. DIP Connections

Q11

VSS

A14

Q15A–1

A15

A16

Q14

A13

BYTEVPP

VSS

Q12

Q10

VCC

A10

A17

AI01635

M27C400

Q13

A12

A11

Table 1. Signal Names

A0-A17

Address Inputs

Q0-Q7

Data Outputs

Q8-Q14

Data Outputs

Q15A–1

Data Output / Address Input

Chip Enable

Output Enable

BYTEVPP

Byte Mode / Program Supply

VCC

Supply Voltage

VSS

Ground

DEVICE OPERATION

The operating modes of the M27C400 are listed in

the Operating Modes Table. A single power supply

is required in the read mode. All inputs are TTL

compatible except for VPP and 12V on A9 for the

Electronic Signature.

Read Mode

The M27C400 has two organisations, Word-wide

and Byte-wide. The organisation is selected by the

signal level on the BYTEVPP pin. When BYTEVPP

is at VIH the Word-wide organisation is selected

and the Q15A–1 pin is used for Q15 Data Output.

When the BYTEVPP pin is at VIL the Byte-wide or-

ganisation is selected and the Q15A–1 pin is used

for the Address Input A–1. When the memory is

logically regarded as 16 bit wide, but read in the

Byte-wide organisation, then with A–1 at VIL the

lower 8 bits of the 16 bit data are selected and with

A–1 at VIH the upper 8 bits of the 16 bit data are

selected.

The M27C400 has two control functions, both of

which must be logically active in order to obtain

data at the outputs. In addition the Word-wide or

Byte-

wide

organisation

must

selected.

Chip Enable (E) is the power control and should be

used for device selection. Output Enable (G) is the

output control and should be used to gate data to

the output pins independent of device selection.

Assuming that the addresses are stable, the ad-

dress access time (tAVQV) is equal to the delay

from E to output (tELQV). Data is available at the

output after a delay of tGLQV from the falling edge

of G, assuming that E has been low and the ad-

dresses have been stable for at least tAVQV-tGLQV.

Standby Mode

The M27C400 has a standby mode which reduces

the supply current from 50mA to 100µA. The

M27C400 is placed in the standby mode by apply-

ing a CMOS high signal to the E input. When in the

standby mode, the outputs are in a high imped-

ance state, independent of the G input.

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