Philips Semiconductors

Product specification

74F670

4 x 4 register file (3-State)

2

1990 Jul 12

853-0014 99965

FEATURES

DESCRIPTION

The 74F670 is a 16-bit 3-State Register File organized as 4 words of

4 bits each. Separate Read and Write Address and Enable inputs

are available, permitting simultaneous writing into one word location

and reading from another location. The 4-bit word to be stored is

presented to four data inputs.

The Write address inputs (WA and WB) determine the location of the

stored word. The Write Address inputs should only be changed

when the Write Enable input (WE) is High for conventional

operation. When the WE is Low, the data is entered into the

addressed location.

The addressed location remains transparent to the data while the

WE is Low. Data supplied at the inputs will be read out in true

(non-inverting) form from the 3-State outputs. Data and address

inputs are inhibited when the WE is High. Direct acquisition of data

stored in any of the four registers is made possible by individual

Read Address inputs (RA, RB). The addressed word appears at the

four outputs when the Read Enable (RE) is Low. Data outputs are in

the high impedance “off” state when the RE is High. This permits

outputs to be tied together to increase the word capacity to very

large numbers.

Up to 128 devices can be stacked to increase the word size to 512

locations by tying the 3-State outputs together. Since the limiting

factor for expansion is the output High current, further stacking is

current available. Design of the Read Enable signals for the stacked

devices must ensure that there is no overlap in the Low levels which

cause more than one output to be active at the same time. Parallel

expansion to generate n-bit words is accomplished by driving the

Enable and address inputs of each device in parallel.

PIN CONFIGURATION

7

14

13

12

11

10

9

6

5

4

3

2

1

D0

WE

RE

Q1

RA

D2

Q3

D1

GND

D3

RB

SF01178

Q0

WB

Q2

WA

8

16

15

TYPE

TYPICAL

PROPAGATION

DELAY

TYPICAL

SUPPLY CURRENT

(TOTAL)

74F670

6.5ns

50mA

ORDERING INFORMATION

DESCRIPTION

COMMERCIAL RANGE

PKG DWG #

16-pin plastic DIP

N74F670N

SOT38-4

16-pin plastic SOL

N74F670D

SOT162-1

INPUT AND OUTPUT LOADING AND FAN-OUT TABLE

PINS

DESCRIPTION

74F(U.L.)

HIGH/LOW

LOAD VALUE

HIGH/LOW

D0 - D3

Data inputs

1.0/1.0

20

µA/0.6mA

WA, WB

Write address inputs

1.0/1.0

20

µA/0.6mA

RA, RB

Read address inputs

1.0/1.0

20

µA/0.6mA

WE

Write Enable inputs

1.0/1.0

20mA/0.6mA

RE

Read Enable inputs

1.0/1.0

20mA/0.6mA

Q0–Q3

Data output

150/40

3.0mA/24mA

NOTE:

One (1.0) FAST Unit Load is defined as: 20

µA in the High state and 0.6mA in the Low state.