AD1816A

–47–

REV. A

PROGRAMMING EXTERNAL EEPROMS

Below are the details for programming an external EEPROM or an ADI-supplied PC Program may be used. The PnP EEPROM can

be written only in the “Alternate Key State”; this prevents accidental EEPROM erasure when using standard PnP setup. The proce-

dure for writing an EEPROM is:

1) Enter PnP configuration state and fully reset the part by writing 0x07 to PnP register 0x02. This step can be eliminated if the part

has not been accessed since power-up, a previous full PnP reset or assertion of the ISA bus RESET signal.

2)Send the alternate initiation key to the PnP address port. EEPROM writes are disabled if the standard PnP key is used.

3)Enter isolation state and write a CSN to enter configuration state. Do not perform any isolation reads.

4)Poll PnP register 0x05 until it equals 0x01 and wait at least 336 microseconds (ensures that EEPROM is idle).

5)Write the second byte of your serial identifier to PnP register 0x20.

6)Read PnP register 0x04.

7)Wait for at least 464 microseconds, plus the EEPROM’s write cycle time (up to 10 ms for a Xicor X24C02).

8)Repeat steps 4 through 7 for each byte in your PnP ROM, starting with the third byte of the serial identifier and ending with the fi-

nal checksum byte. You must then continue to write filler bytes until 512 bytes, minus one more than the number of flag bytes, have

been written. Finally, write the flag byte(s) (described above) and the first byte of the serial identifier.

9) Fully reset the part by writing 0x07 to PnP register 0x02.

The AD1816 or AD1816A will now act according to the contents of the EEPROM.

NOTES

Programming will not work if more than one part uses the same alternate initiation key in the system. Parts that use this alternate

initiation key are the AD1816 and AD1816A.

If a 256-byte EEPROM is used, it is not necessary to wait 10 ms after writing bytes 255 to 511, because the EEPROM will ignore

them anyway.

You can skip over bytes that you don’t care to write by just performing a ROM read instead of a ROM write followed by a ROM read.

REFERENCE DESIGNS AND DEVICE DRIVERS

Reference designs and device drivers for the AD1816A are available via the Analog Devices Home Page on the World Wide Web at

http://www.analog.com. Reference designs may also be obtained by contacting your local Analog Devices Sales representative or

authorized distributor.