Functional Description
Each FIFO has support for generating interrupts when the FIFO word count has reached a programmable
threshold level. The user can program these registers to the desired word count at which the CPU should
be interrupted. Whenever the threshold counter value is reached, it sets the FIFO THRESHOLD interrupt
flag, and the CPU is interrupted if the FIFO THRESHOLD interrupt enable bit is set. The user can clear
the interrupt flag, after emptying the FIFO, by writing a ‘1’ to the FIFO TRESHOLD interrupt status bit. To
determine how many samples are currently in the FIFO at a given moment, the FIFO_WORD_COUNT
register can be read by the CPU.
The FIFO can also generate FIFO_OVERRUN and FIFO_UNDERFLOW interrupts. The user can mask
these events by programming the enable bits. To clear a FIFO underflow or FIFO overrun interrupt, the
user should write a ‘1’ so the status bit. The TSC_ADC_SS does not recover from these conditions
automatically. Therefore, the software will need to disable and then again enable the TSC_ADC_SS.
Before user can turn the module back on, he must first check if the ADC FSM is in IDLE state by reading
from the ADC_STATUS_REG register.
12.3.6 DMA Requests
Each FIFO group can be serviced by either a DMA or by the CPU. To generate DMA requests, the user
must set the enable bit in the DMAENABLE_SET Register. Also, the user can program the desired
number of words to generate a DMA request using the DMAxREQ register. When the FIFO level reaches
or exceeds that value, a DMA request is generated.
The DMA slave port allows for burst reads in order to effectively move the FIFO data. Internally, the OCP
DMA address (MSB) is decoded for either FIFO 0 or FIFO 1. The lower bits of the DMA addresses are
ignored since the FIFO pointers are incremented internally.
12.3.7 Analog Front End (AFE) Functional Block Diagram
The AFE features are listed below, and some are controlled by the TSC_ADC_SS:
•
12-bit ADC
•
Sampling rate can be as fast as every 15 ADC clock cycles
•
Support for internal ADC clock divider logic
•
Support for configuring the delay between samples also the sampling time
1027
SPRUH73H – October 2011 – Revised April 2013
Touchscreen Controller
Copyright © 2011–2013, Texas Instruments Incorporated