CS8405A

DS469PP4

25

INT

19

Interrupt (Output) - Indicates key events during the operation of the CS8405A. All bits affecting INT

may be unmasked through bits in the control registers. Indication of the condition(s) that initiated an

interrupt are readable in the control registers. The polarity of the INT output, as well as selection of a

standard or open drain output, is set through a control register. Once set true, the INT pin goes false

only after the interrupt status registers have been read and the interrupt status bits have returned to

zero.

U

20

User Data (Input/Output) - May optionally be used to input User data for transmission by the AES3

transmitter, see Figure 7 for timing information. Alternatively, the U pin may be set to output, which also

selects the internal buffer as the source of transmitted U data. If not driven, a 47 k

Ω pull-down resistor is

recommended for the U pin, because the default state of the UD direction bit sets the U pin as an input.

The pull-down resistor ensures that the transmitted user data will be zero. If the U pin is always set to be

an output, thereby causing the U bit manager to be the source of the U data, then the resistor is not nec-

essary. The U pin should not be tied directly to ground, in case it is programmed to be an output, and

subsequently tries to output a logic high. This situation may affect the long term reliability of the device.

If the U pin is driven by a logic level output, then a 100

Ω series resistor is recommended.

OMCK

21

Master Clock (Input) - The frequency must be 256x, 384x, or 512x the sample rate.

H/S

24

Hardware/Software Control Mode Select (Input) -Determines the method of controlling the operation

of the CS8405A, and the method of accessing Channel Status and User bit data. In software mode,

device control and CS and U data access is primarily through the control port, using a microcontroller.

Hardware mode provides an alternate mode of operation, and access to CS and U data is provided by

dedicated pins. This pin should be permanently tied to VL+ or DGND.

TXN

25

26

Differential Line Drivers (Output) - Transmitting AES3 data. Drivers are pulled low while the CS8405A

is in the reset state.

TXP

AD1/CDIN

27

Address Bit 1 (Two-Wire Mode) / Serial Control Data in (SPI) (Input) - In Two-Wire mode, AD1 is a

chip address pin. In SPI mode, CDIN is the input data line for the control port interface.

SCL/CCLK

28

Control Port Clock (Input) - Serial control interface clock and is used to clock control data bits into and

out of the CS8405A. In Two-Wire mode, SCL requires an external pull-up resistor to VL+.