2

Functional Diagram

MODE SELECT FUNCTION TABLE THREE-STATE I/O PORT OPERATING MODE

FUNCTION

INPUTS

INPUTS/OUTPUTS

OE1

OE2

S0

S1

Qn (REGISTER)

I/O0 --- I/O7

Read Register

L

L

L

X

L

L

L

LL

XH

H

LL

X

L

L

L

LL

X

L

H

H

Load Register

X

X

H

H

Qn = I/On

I/On = Inputs

Disable I/O

H

X

X

X

X

(Z)

XHX

X

X

(Z)

TRUTH TABLE

FUNCTION

INPUTS

REGISTER OUTPUTS

MR

CP

S0

S1

DS0

DS7

I/On

Q0

Q1

---

Q6

Q7

RESET (CLEAR)

L

XXXXXX

L

L

---

L

L

Shift Right

H

↑

hl

l

X

X

L

q0

---

q5

q6

H

↑

hlh

X

X

H

q0

---

q5

Q6

Shift Left

H

↑

l

h

XlX

q1

q2

---

q7

L

H

↑

lh

X

h

X

q1

q2

---

q7

H

Hold (Do Nothing)

H

↑

l

l

XXX

q0

q1

---

q6

q7

Parallel Load

H

↑

hh

X

X

l

L

L

---

LL

H

↑

h

h

X

X

h

H

H

---

H

H

H = Input Voltage High Level, h = Input voltage high one set-up timer prior clock transition; L = Input Voltage Low Level; l = Input voltage

low one set-up time prior to clock transition; qn = Lower case letter indicates the state of the reference output one set-up time prior to clock

transition; X - Voltage level on logic status don’t care; Z = Output in high impedance state,

↑ = Low to High Clock Transition.

I/O

THREE-STATE

OUTPUTS

I/O

THREE-STATE

OUTPUTS

SHIFT

REGISTER

MODE SELECTION

CP OE1 OE2

MR

12

2

3

9

20

VCC

7

6

5

4

8

1

I/O0

Q0

S0

STANDARD

OUTPUT

I/O2

I/O4

I/O6

BUS LINE

OUTPUTS

GND

10

11

18

DS0

DS7

13

14

15

16

17

19

I/O1

Q7

S1

STANDARD

OUTPUT

I/O3

I/O5

I/O7

BUS LINE

OUTPUTS

THREE-

STATE

CONTROL

CD54HC299, CD74HC299, CD54HCT299, CD74HCT299