4-Wire Interfaced, 2.7V to 5.5V,

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13

Table 18 shows an example of data (characters 0, 1,

and 2) being stored in the first three user-defined font

locations, illustrating the orientation of the data bits.

Table 19 shows the six sequential write commands

required to set a MAX6953's font character RAM02 with

the data to display character 2 given in the font RAM

illustration above.

Multiplex Clock and Blink Timing

(to use the internal RC multiplex oscillator), or driven by

an external clock. The multiplex clock frequency deter-

mines the multiplex scan rate and the blink timing. The

display scan rate is calculated by dividing the frequency

at OSC by 5600. With OSC at 4 MHz, each display digit

is enabled for 100µs and the display scan rate is

714.29Hz.

The on-chip oscillator may be accurate enough for

applications using a single device. If an exact blink rate

is required, use an external clock ranging between

1MHz and 8MHz to drive OSC. The OSC inputs of multi-

ple MAX6952s can be tied together to a common exter-

nal clock to make the devices blink at the same rate.

The relative blink phasing of multiple MAX6952s can be

synchronized by setting the T bit in the control register

for all the devices in quick succession (Table 11).

If the serial interfaces of multiple MAX6952s are daisy-

chained by connecting DOUT of one device to DIN of

the next, then synchronization is achieved automatically

by updating the control register for all devices together.

For MAX6952s, the devices can be synchronized by

transmitting the serial data for the control register, and

then toggling the CS pin for each device, either togeth-

er or in quick succession. Figure 7 is the multiplex tim-

ing diagram.

Blink Output

The blink output indicates the blink phase, and is high

during the P0 period and low during the P1 period.

Blink phase status can also be read back as the P bit in

the configuration register (Table 13). Typical uses for

this output are:

• To provide an interrupt to the processor so that seg-

ment data can be changed synchronous to the

blinking. For example, a clock application may have

colon segments blinking every second between

hours and minute digits, and the minute display is

best changed in step with the colon segments. Also,

if the rising edge of blink is detected, there is half a

blink period to change the P1 digit data. Similarly, if

the falling edge of blink is detected, the user has

half a blink period to change the P0 digit data.

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 14. Character Map