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Conversion Controlled by TSC2301 Initiated By Host Responding to PENIRQ

TSC2301

SLAS371D – SEPTEMBER 2002 – REVISED AUGUST 2004

This mode is provided for users who want more control over the A/D conversion process. This mode requires

more overhead from the host processor, so it is generally not recommended.

In this mode, the TSC2301 detects when the touch panel is touched and causes the PENIRQ line to go low. The

host recognizes the interrupt request, and then writes to the ADC control register to select one of the touch

screen scan functions (single X-, Y-, or Z-conversions, continuous X/Y or X/Y/Z1/Z2 Conversions). The

conversion process then proceeds as described above, and as outlined in Figure 53 through Figure 57 .

The main difference between this mode and the previous mode is that the host, not the TSC2301, decides when

the touch screen scan begins after responding to a PENIRQ. In this mode, the host must either monitor both

PENIRQ and DAV, or wait a minimum time after writing to the A/D converter control register. This wait time can

be calculated from Equation 6 in the case of single conversions, or from Equation 4 or Equation 5 in the case of

multiple conversions. The nominal conversion times calculated by these equations should be extended by

approximately 12% to account for variation in the internal oscillator frequency.