Serially Interfaced, 8-Digit LED Display Drivers
MAX7219/MAX7221
Table 7. Intensity Register Format (Address (Hex) = 0xXA)
DUTY CYCLE
MAX7219
1/32
(min on)
3/32
5/32
7/32
9/32
11/32
13/32
15/32
17/32
19/32
21/32
23/32
25/32
27/32
29/32
31/32
MAX7221
1/16
(min on)
2/16
3/16
4/16
5/16
6/16
7/16
8/16
9/16
10/16
11/16
12/16
13/16
14/16
15/16
15/16
(max on)
D7
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
D6
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
D5
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
D4
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
D3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
D2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
D1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
D0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
HEX
CODE
0xX0
0xX1
0xX2
0xX3
0xX4
0xX5
0xX6
0xX7
0xX8
0xX9
0xXA
0xXB
0xXC
0xXD
0xXE
0xXF
Table 8. Scan-Limit Register Format (Address (Hex) = 0xXB)
SCAN LIMIT
Display digit 0 only*
Display digits 0 & 1*
Display digits 0 1 2*
Display digits 0 1 2 3
Display digits 0 1 2 3 4
Display digits 0 1 2 3 4 5
Display digits 0 1 2 3 4 5 6
Display digits 0 1 2 3 4 5 6 7
REGISTER DATA
D7
X
X
X
X
X
X
X
X
D6
X
X
X
X
X
X
X
X
D5
X
X
X
X
X
X
X
X
D4
X
X
X
X
X
X
X
X
D3
X
X
X
X
X
X
X
X
D2
0
0
0
0
1
1
1
1
D1
0
0
1
1
0
0
1
1
D0
0
1
0
1
0
1
0
1
HEX
CODE
0xX0
0xX1
0xX2
0xX3
0xX4
0xX5
0xX6
0xX7
*See
Scan-Limit Register
section for application.
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
rate is 8f
OSC
/N, where N is the number of digits
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.
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
