Datasheet

Initial Power-Up
On initial power-up, all control registers are reset, the
display is blanked, and the MAX7219/MAX7221 enter
shutdown mode. Program the display driver prior to
display use. Otherwise, it will initially be set to scan one
digit, it will not decode data in the data registers, and
the intensity register will be set to its minimum value.
Decode-Mode Register
The decode-mode register sets BCD code B (0-9, E, H,
L, P, and -) or no-decode operation for each digit. Each
bit in the register corresponds to one digit. A logic high
selects code B decoding while logic low bypasses the
decoder. Examples of the decode mode control-regis-
ter format are shown in Table 4.
When the code B decode mode is used, the decoder
looks only at the lower nibble of the data in the digit
registers (D3–D0), disregarding bits D4–D6. D7, which
sets the decimal point (SEG DP), is independent of the
decoder and is positive logic (D7 = 1 turns the decimal
point on). Table 5 lists the code B font.
When no-decode is selected, data bits D7–D0 corre-
spond to the segment lines of the MAX7219/MAX7221.
Table 6 shows the one-to-one pairing of each data bit
to the appropriate segment line.
Serially Interfaced, 8-Digit LED Display Drivers
Table 2. Register Address Map
Table 3. Shutdown Register Format (Address (Hex) = 0xXC)
Table 4. Decode-Mode Register Examples (Address (Hex) = 0xX9)
No-Op X 0 0
0
0
0
ADDRESS
0
1
0xX0
0xX1
Digit 1 X 0 0
0
1
1
0
1
0xX2
0
0xX30Digit 2 X
Digit 3 X 0 1
1
0
Digit 0 X
0
0
1
0xX4
0xX5
Digit 5 X 0 1
1
1
1
0
1
0xX6
0
0xX70Digit 6 X
Digit 4 X
Digit 7 X 1 0
0
0
0
0
1
0xX8
0xX91
Decode
Mode
X
Intensity X 1 0
0
1
1
0
1
0xXA
0xXB
Shutdown X 1 1
1
0
1
0
1
0xXC
1
0xXF1
Display
Test
X
Scan Limit X
D15–
D12
D11 D10
REGISTER
D9 D8
HEX
CODE
X
Shutdown
Mode
0xXC X
X
XX
XX
XX
X
0X
1XXX
REGISTER DATA
MODE
Normal
Operation
0xXC
0No decode for digits 7–0 0
0
1
D7
DECODE MODE
0 0x000
0
1
D6 D5
0
1
D4 D3
0
1Code B decode for digits 7–0
Code B decode for digit 0
No decode for digits 7–1
0 0
0
1
D2
HEX
CODE
0
REGISTER DATA
0
0xFF
1
1
D1 D0
0
1
0
1
0 00
0x01
0
Code B decode for digits 3–0
No decode for digits 7–4
1 111 0x0F
ADDRESS CODE
(HEX)
D6 D4D7 D5 D2 D0D3 D1
MAX7219/MAX7221
Maxim Integrated
7