Matrix LED Display Driver

14

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Global Clear Digit Data (R Data Bit D5) Format

When global digit data clear is set, the digit data for

both planes P0 and P1 for all digits are cleared during

the acknowledge (Table 13).

Blink Phase Readback (P Data Bit D7) Format

When the configuration register is read, the P bit

reflects the state of the blink output pin at that time

(Table 14).

Character Generator Font Mapping

ROM, and 24 user-definable characters. The selection

from the total of 128 characters is represented by the

lower 7 bits of the 8-bit digit registers. The most-signifi-

cant bit, shown as x in the ROM map, is zero to light

LEDs as shown by the black segments in Table 15, and

1 to display the inverse.

The character map follows the Arial font for 96 charac-

ters in the range 0x0101000 through x1111111. The

first 32 characters map the 24 user-definable positions

(RAM00 to RAM23), plus eight extra common charac-

ters in ROM.

User-Defined Fonts

The 24 user-definable characters are represented by

120 entries of 7-bit data, five entries per character, and

are stored in MAX6953's internal RAM.

The 120 user-definable font data entries are written and

read through a single register, address 0x05. An

autoincrementing font address pointer in the MAX6953

indirectly accesses the font data. The font address

pointer can be written, setting one of 120 addresses

between 0x00 and 0xF7, but cannot be read back. The

font data is written to and read from MAX6953 indirect-

ly, using this font address pointer. Unused font loca-

tions can be used as general-purpose scratch RAM,

bearing in mind that the font registers are only 7 bits

wide, not 8.

Table 16 shows how the single user-defined font regis-

ter 0x05 is used to set the font address pointer, write

font data, and read font data. A read action always

returns font data from the font address pointer position.

A write action sets the 7-bit font address pointer if the

MSB is set, or writes 7-bit font data to the font address

pointer position if the MSB is clear.

The font address pointer autoincrements after a valid

access to the user-definable font data. Auto-

incrementing allows the 120 font data entries to be writ-

ten and read back very quickly because the font point-

er address need only be set once. When the last data

location 0xF7 is written, the font address pointer autoin-

crements to address 0x80. If the font address pointer is

0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

x000

x001

x010

x011

x100

x101

x110

x111

RAM00

RAM01

RAM02

RAM03

RAM04

RAM05

RAM06

RAM07

MSB

LSB

RAM08

RAM09

RAM10

RAM11

RAM12

RAM13

RAM14

RAM15

RAM16

RAM17

RAM18

RAM19

RAM20

RAM21

RAM22

RAM23

Table 15. Character Map