Datasheet

2−26

samples must be logic 0 before a logic 0 is read. A read logic 0 on a given GPIO port is interpreted as a command

to increase or decrease volume. If a logic 0 is read, and the signal level into the GPIO port remains at logic 0 for another

GPIO_samp_int consecutive samples, a second logic 0 value is read.

For each logic 0 read, the volume is increased or decreased 0.5 dB. After two consecutive logic 0 readings, each logic

0 reading that follows results in the volume level increasing or decreasing 5 dB instead of 0.5 dB. Figure 2−22 shows

an example of activating a volume switch. For the example in Figure 2−22, GPIOFSCOUNT is set to 3 and

GPIO_samp_int is set to 2. It is also noted in Figure 2−22 that the parameter GPIO_samp_int only comes into play

on logic 0 valued samples. As soon as the GPIO sample goes to logic 1, the audio updating ceases.

2.8.2 GPIO Functionality—I

C Slave Mode

In the I

C slave mode, the GPIO ports can be used as true general-purpose ports. Each port can be individually

programmed, via the I

C bus, to be either an input or an output port. The default assignment for all GPIO ports, in

the I

C slave mode, is an input port.

When a given GPIO port is programmed as an output port, by setting the appropriate bit in the bit field GPIODIR

(19:16) of subaddress 0xEF to logic 1, the logic level output is set by the logic level programmed into the appropriate

bit in bit field GPIO_in_out (3:0) of subaddress 0xEE. The I

C bus then controls the logic output level for those GPIO

ports assigned as output ports.

When a given GPIO port is programmed as an input port by setting the appropriate bit in bit field GPIODIR (19:16)

of subaddress 0xEF to logic 0, the logic input level into the GPIO port is written to the appropriate bit in bit field

GPIO_in_out (3:0) of subaddress 0xEE. The I

C bus can then be used to read bit field GPIO_in_out to determine

the logic levels at the input GPIO ports. Whether a given bit in the bit field GPIO_in_out is a bit to be read via the I

bus or a bit to be written to via the I

C bus is strictly determined by the corresponding bit setting in bit field GPIODIR.

In the I

C slave mode, the GPIO input ports are read every GPIOFSCOUNT LRCLKs, as was the case in the I

master mode. However, parameter GPIO_samp_int does not have a role in the I

C slave mode. If a GPIO port is

assigned as an output port, a logic 0 bit value is supplied by the TAS3103 for this GPIO port in response to a read

transaction at subaddress 0xEE.

If the GPIO ports are left in their power turnon state default state, they are input ports with a weak pullup on the input

to VDSS.