Matrix LED Display Driver

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9

read-after-write verification, reset the command byte's

address because the stored byte address generally is

autoincremented after the write (Table 4).

Operation with Multiple Masters

If the MAX6953 is operated on a 2-wire interface with

multiple masters, a master reading the MAX6953

should use a repeated start between the write, which

sets the MAX6953's address pointer, and the read(s)

that takes the data from the location(s). This is because

it is possible for master 2 to take over the bus after

master 1 has set up the MAX6953's address pointer but

before master 1 has read the data. If master 2 subse-

quently changes the MAX6953's address pointer, then

master 1's delayed read may be from an unexpected

location.

Command Address Autoincrementing

Address autoincrementing allows the MAX6953 to be

configured with the shortest number of transmissions

by minimizing the number of times the command byte

needs to be sent. The command address or the font

pointer address stored in the MAX6953 generally incre-

ments after each data byte is written or read (Table 4).

Digit Registers

The MAX6953 uses eight digit registers to store the char-

LED digits. These digit registers are implemented with

two planes of 4 bytes, called P0 and P1. Each LED digit

is represented by 2 bytes of memory, 1 byte in plane P0

and the other in plane P1. The digit registers are mapped

so that a digit’s data can be updated in plane P0, or

plane P1, or both planes at the same time (Table 5).

If the blink function is disabled through the Blink Enable

Bit E (Table 10) in the configuration register, then the

digit register data in plane P0 is used to multiplex the

display. The digit register data in P1 is not used. If the

blink function is enabled, then the digit register data in

both plane P0 and plane P1 are alternately used to mul-

tiplex the display. Blinking is achieved by multiplexing

the LED display using data planes P0 and P1 on alter-

nate phases of the blink clock (Table 11).

The data in the digit registers does not control the digit

segments directly. Instead, the register data is used to

address a character generator, which stores the data of

a 128-character font (Table 15). The lower 7 bits of the

digit data (D6 to D0) select the character from the font.

The most-significant bit of the register data (D7) selects

whether the font data is used directly (D7 = 0) or

whether the font data is inverted (D7 = 1). The inversion

feature can be used to enhance the appearance of

bicolor displays by displaying, for example, a red char-

acter on a green background.

Display Blink Mode

The display blinking facility, when enabled, makes the

driver flip automatically between displaying the digit

register data in planes P0 and P1. If the digit register

data for any digit is different in the two planes, then that

SA

A

P

0

SLAVE ADDRESS

COMMAND BYTE

ACKNOWLEDGE FROM MAX6953

R/W

ACKNOWLEDGE FROM MAX6953

D15

D14

D13

D12

D11

D10

D9

D8

COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION

Figure 7. Command Byte Received

AA

AP

0

SLAVE ADDRESS

COMMAND BYTE

DATA BYTE

ACKNOWLEDGE FROM MAX6953

R/W

1 BYTE

AUTOINCREMENT MEMORY WORD ADDRESS

ACKNOWLEDGE FROM MAX6953

ACKNOWLEDGE FROM MAX6953

D15

D14

D13

D12

D11

D10

D9

D8

D1

D0

D3

D2

D5

D4

D7

D6

HOW CONTROL BYTE AND DATA BYTE MAP INTO

MAX6953's REGISTERS

S

Figure 8. Command and Single Data Byte Received