Datasheet
2−27
The watchdog timer is governed by the parameter GPIOFSCOUNT in subaddress 0xEF and the LSB of the 32-bit
word at subaddress 0xEB. The default value of the LSB of the 32-bit word at subaddress 0xEB is 1, and this value
disables the watchdog timer. The GPIOFSCOUNT is also used in other functions and balancing the needs of these
other functions regarding GPIOFSCOUNT with the requirements of the watchdog timer is an involved process. For
this reason, it is strongly recommended that the LSB of the 32-bit word at subaddress 0xEB remain a 1. If an
application does require use of the watchdog timer, it is requested that the user contact an application engineer in
the Digital Audio Department of Texas Instruments for details in properly using this feature.
2.8 General-Purpose I/O (GPIO) Ports
The TAS3103A has four general-purpose I/O (GPIO) ports. Figure 2−23 is a block diagram of the GPIO circuitry in
the TAS3103A.
GPIO0
GPIO1
GPIO2
GPIO3
D
Q
D
Q
D
Q
D
Q
Sample
Logic
0xEF
Down
Counter
LD
LRCLK
Decode 0
DATA PATH SWITCH
GPIODIR
3
Determines How Many Consecutive Logic-0 Samples
(Where Each Sample Is Spaced by GPIOFSCOUNT
LRCLKs) are Required to Read a Logic 0 on a
GPIO Input Port
S Slave Addr SubaddrAck 00000000Ack
Ack
210
0000
Ack
GPIOFSCOUNT
Ack
GPIO_samp_int
Ack
31 24 23 20 19 16 15 8 7 0
Microprocessor
Microprocessor
Firmware
Microprocessor
Control
0xEE
GPIO_in_out
3
S Slave Addr SubaddrAck 00000000Ack
Ack
210
Ack
31 24 23 16 0
00000000
15 8
00000000
Ack
74
0000
Ack
3
I
2
C Slave Mode
and
I
2
C Master Mode
Write
I
2
C Master
Mode Read
Figure 2−23. GPIO Port Circuitry
2.8.1 GPIO Functionality—I
2
C Master Mode
In the I
2
C master mode, the GPIO ports are strictly input ports and are used to control volume. Table 2−6 lists the
functionality of each GPIO port in the I
2
C master mode. Bit field GPIOFSCOUNT (15:8) of I
2
C subaddress 0xEF
governs the rate at which the GPIO pins are sampled for a volume update. The sample rate is:
ƒ
GPIO_Port
+
LRCLK
GPIOFSCOUNT