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-register 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 correspond
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.
Table 2. Register Address Map
Table 3. Shutdown Register Format (Address (Hex) = 0xXC)
Table 4. Decode-Mode Register Examples (Address (Hex) = 0xX9)
REGISTER
ADDRESS
HEX
CODE
D15–
D12
D11 D10 D9 D8
No-Op X 0 0 0 0 0xX0
Digit 0 X 0 0 0 1 0xX1
Digit 1 X 0 0 1 0 0xX2
Digit 2 X 0 0 1 1 0xX3
Digit 3 X 0 1 0 0 0xX4
Digit 4 X 0 1 0 1 0xX5
Digit 5 X 0 1 1 0 0xX6
Digit 6 X 0 1 1 1 0xX7
Digit 7 X 1 0 0 0 0xX8
Decode
Mode
X 1 0 0 1 0xX9
Intensity X 1 0 1 0 0xXA
Scan Limit X 1 0 1 1 0xXB
Shutdown X 1 1 0 0 0xXC
Display
Test
X 1 1 1 1 0xXF
MODE
ADDRESS CODE
(HEX)
REGISTER DATA
D7 D6 D5 D4 D3 D2 D1 D0
Shutdown Mode 0xXC X X X X X X X X
Normal Operation 0xXC X X X X X X X 1
DECODE MODE
REGISTER DATA
HEX
CODE
D7 D6 D5 D4 D3 D2 D1 D0
No decode for digits 7–0 0 0 0 0 0 0 0 0 0x00
Code B decode for digit 0
No decode for digits 7–1
0 0 0 0 0 0 0 1 0x01
Code B decode for digits 3–0
No decode for digits 7–4
0 0 0 0 1 1 1 1 0x0F
Code B decode for digits 7–0 1 1 1 1 1 1 1 1 0xFF
MAX7219/MAX7221 Serially Interfaced, 8-Digit LED Display Drivers
www.maximintegrated.com
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