AD1816A

–42–

REV. A

AD1816 AND AD1816A COMPATIBILITY

The AD1816 and AD1816A are pin for pin and functionally compatible. The AD1816A may be dropped directly into an existing

AD1816 design. However, the AD1816A has greater pin assignment flexibility to accommodate a wider range of applications and for

controlling extra logical devices such as a modem chip set or an Enhanced IDE controller. Pin assignments are controlled by the ex-

ternal EEPROM. Consequently, the optional EEPROM must be reprogrammed to configure the AD1816A.

USING AN EEPROM WITH THE AD1816 OR AD1816A

The AD1816 and AD1816A support an optional Plug and Play resource ROM. If present, the ROM must be a two-wire serial de-

vice (e.g. Xicor X24C02) and the clock and data lines should be wired to EE_CLK and EE_DATA pins; pull-up resistors are re-

quired on both signals. The EEPROM’s A2 and A1 pins (also A0 for 256-byte EEPROMs) must all be tied to ground. The write

control pin (WC*) must be tied to power if you wish to program the EEPROM in place; otherwise, we recommend tying it to ground

to prevent accidental writes.

The EEPROM interface logic examines the state of the EE_CLK pin shortly after RESET is deasserted and whenever the Plug and

Play reset register (02h) is written with a value X such that ([X & 1]

≠ 0). If an EEPROM is connected, EE_CLK is pulled high and

the EEPROM logic attempts to read the first ROM byte (page 0, byte 0). If EE_CLK is tied low, the internal ROM is used; in this

case EE_DATA is used to set the state of VOL_EN, and should also be tied high or low. EE_CLK is not used as an input at any

other time.

The initial part of the ROM is not part of the Plug and Play resource data. It consists of a number of flags that enable optional func-

tionality. The number of flag bytes and the purpose of each bit depend on whether an AD1816 or an AD1816A is being used.

AD1816 FLAG BYTE

The AD1816 has a single flag byte that is used as shown below:

76543210

100

XTRA_SIZE

VOL_SEL

VOL_EN

XTRA_IRQ

XTRA_EN

MODEM_EN

MODEM_EN

Program to one to enable the modem logical device. This logical device has an I/O range and an IRQ. The I/O

range has the following requirements:

– Length of eight bytes

– Alignment of eight bytes

– 16-bit address decode

Program to zero to enable I

XTRA_EN

Program to one to enable the XTRA logical device. This logical device has an I/O range, an optional IRQ, and an

optional DMA. The I/O range has the following requirements:

– Length of eight bytes or 16 bytes, selectable by XTRA_SIZE

– Alignment of eight bytes or 16 bytes, matches length

– 16-bit address decode

Program to zero to enable the DSP serial port.

XTRA_IRQ

Program to one to include an IRQ in the XTRA logical device. When enabled, the IRQ level and type are pro-

grammed through PnP registers 0x70 and 0x71. (Note: For the 1816, the IRQ type is hard coded and rising edge

triggered.)

VOL_EN

Program to one to enable hardware volume control.

XTRA_SIZE/

The function of this bit depends on XTRA_EN. If XTRA_EN is one, this bit selects the size of the XTRA

VOL_SEL

device’s I/O range. Program to one to make the XTRA logical device I/O length 16 bytes. Program to zero to set

the XTRA logical device I/O length to eight bytes. The alignment specified in the resource data must be an integer

multiple of the length. If XTRA_EN is zero (and VOL_EN is one), then this bit selects the location of the hard-

ware volume control pins. Program to zero to replace I

place the SPORT.

The three MSBs in the first byte of the AD1816 EEPROM are used to verify that the EEPROM data is valid. The bits are compared

to the values shown; if a mismatch is found, then the EEPROM will be ignored. The internal ROM will be used to perform PnP

enumeration, and the MODEM and XTRA logical devices will not be available. Hardware volume will be enabled on the I

The SPORT is disabled.

USING THE AD1816 WITHOUT AN EEPROM

If the EEPROM is absent (EE_CLK pin = GND), the flags are set as shown below:

MODEM_EN = XTRA_EN = XTRA_IRQ = VOL_SEL = 0

VOL_EN = EE_DATA pin