ASAHI KASEI

[AK9822/24]

DAD01E-00

1999/05

- 3 -

Functional Description

The AK9822/24 is composed of EEPROM and the 8bit D/A converter of two channels with the

output buffer amplifier.

The AK9822/24 can connect to the serial communication port of popular one chip microcomputer

directly (3 line negative clock synchronous interface).

The AK9822/24 takes the data of the DI pin by the rising edge of the SK pin and outputs the data

from the DO pin by the falling edge of the SK pin.

The AK9822/24 has 7 instructions such as READ, WRITE, WREN, WRDS, PDEN, PDDS and CALL.

The AK9822/24 is operated by inputting these instructions from the serial interface. Each instruction

is organized by op-code block (8bits), address block (8bits) and data (8bits

Õ2).

The DO pin is "Hi-Z" state except that the DO pin outputs the data of the internal register and the

status of Ready/Busy.

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„ WRITE protection function

There are two states such as the WRITE enable state and the WRITE disable state in the

AK9822/24. In the WRITE disable state the WRITE instruction becomes invalid and is not executed.

When Vcc is applied to the part, the part powers up in the WRITE disable state and the part

becomes the WRITE enable state by inputting the WREN instruction. The WRITE enable state

continues until the WRDS instruction is executed or Vcc is removed from the part.

Execution of a READ instruction is independent of both WREN and WRDS instructions.

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„ Power down function

There are two modes such as the power down mode and the normal mode in the AK9822/24. When

the AK9822/24 is in the power down mode, the D/A converter section is in the standby state. At this

time, the outputs of the D/A converters become "Hi-Z".

When Vcc is applied to the part, the AK9822/24 is in the power down mode. When a AUTO READ

function is executed, the part becomes the normal mode. After the AUTO READ function is

executed, the mode of the part can be switched by the PDEN and PDDS instructions. The

AK9822/24 becomes the power down mode by inputting the PDEN instruction. The part is in the

power down mode until the PDDS instruction is executed. When the PDDS instruction is executed,

the part becomes the normal mode.

When returning to the normal mode from the power down mode, the D/A converters output the

voltage value set before entering the power down mode. The relation between the D/A converter

state and the mode are shown in the table 1.

Mode

State of D/A converter

Power down mode

standby

Normal mode

normal

Table 1. The relation between the state of D/A converter and the mode