Scan-Limit Register

The scan-limit register sets how many digits are dis-

played, from 1 to 8. They are displayed in a multiplexed

manner with a typical display scan rate of 800Hz with 8

digits displayed. If fewer digits are displayed, the scan

scanned. Since the number of scanned digits affects

the display brightness, the scan-limit register should

not be used to blank portions of the display (such as

leading zero suppression). Table 8 lists the scan-limit

register format.

Serially Interfaced, 8-Digit LED Display Drivers

_______________________________________________________________________________________

9

Table 7. Intensity Register Format (Address (Hex) = XA)

DUTY CYCLE

MAX7221

MAX7219

D6

D7

D4

D2

D3

D0

D5

D1

HEX

CODE

1/16

(min on)

1/32

(min on)

X

X

X

X

0

0

0

0

X0

2/16

3/32

X

X

X

X

0

0

1

0

X1

3/16

5/32

X

X

X

X

0

0

0

1

X2

4/16

7/32

X

X

X

X

0

0

1

1

X3

5/16

9/32

X

X

X

X

1

0

0

0

X4

6/16

11/32

X

X

X

X

1

0

1

0

X5

7/16

13/32

X

X

X

X

1

0

0

1

X6

X

8/16

15/32

X

X

X

X

1

0

1

1

X7

9/16

17/32

X

X

X

X

0

1

0

0

X8

10/16

19/32

X

X

X

X

0

1

1

0

X9

11/16

21/32

X

X

X

X

0

1

0

1

XA

12/16

23/32

X

X

X

X

0

1

1

1

XB

13/16

25/32

X

X

X

X

1

1

0

0

XC

14/16

27/32

X

X

X

X

1

1

1

0

XD

15/16

29/32

X

X

X

X

1

1

0

1

XE

15/16

(max on)

31/32

X

X

X

1

1

1

1

XF

Table 8. Scan-Limit Register Format (Address (Hex) = XB)

X

X

Display digit 0 only*

Display digits 0 & 1*

X

X

X

D7

SCAN LIMIT

X1

X

X0

X

X

X

0

D6

D5

0

1

D4

D3

X

X

Display digits 0 1 2*

Display digits 0 1 2 3

X

X

X

X

0

X3

X

D2

HEX

CODE

X2

0

REGISTER DATA

0

X

X

X

D1

D0

0

1

1

X

0

1

0

X

X

Display digits 0 1 2 3 4

Display digits 0 1 2 3 4 5

X

X

X

X5

X

X4

X

X

X

1

0

1

X

X

Display digits 0 1 2 3 4 5 6

Display digits 0 1 2 3 4 5 6 7

X

X

X

X

1

X7

X

X6

0

0

X

X

X

1

1

1

X

1

1

0

*See

Scan-Limit Register section for application.