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

_______________________________________________________________________________________

7

Table 2. Register Address Map

Table 3. Shutdown Register Format (Address (Hex) = XC)

Table 4. Decode-Mode Register Examples (Address (Hex) = X9)

No-Op

X

0

0

0

0

0

ADDRESS

0

1

X0

X1

Digit 1

X

0

0

0

1

1

0

1

X2

0

X3

0

Digit 2

X

Digit 3

X

0

1

1

0

Digit 0

X

0

0

1

X4

X5

Digit 5

X

0

1

1

1

1

0

1

X6

0

X7

0

Digit 6

X

Digit 4

X

Digit 7

X

1

0

0

0

0

0

1

X8

X9

1

Decode

Mode

X

Intensity

X

1

0

0

1

1

0

1

XA

XB

Shutdown

X

1

1

1

0

1

0

1

XC

1

XF

1

Display

Test

X

Scan Limit

X

D15–

D12

D11

D10

REGISTER

D9

D8

HEX

CODE

X

Shutdown

Mode

XC

X

X

X

X

X

X

X

X

X

0

X

1

X

X

X

REGISTER DATA

MODE

Normal

Operation

XC

0

No decode for digits 7–0

0

0

1

D7

DECODE MODE

0

00

0

0

1

D6

D5

0

1

D4

D3

0

1

Code 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

FF

1

1

D1

D0

0

1

0

1

0

0

0

01

0

Code B decode for digits 3–0

No decode for digits 7–4

1

1

1

1

0F

ADDRESS CODE

(HEX)

D6

D4

D7

D5

D2

D0

D3

D1