TSC2004 datasheet(36/62 Pages) TI2

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TSC2004

SBAS408E – JUNE 2007 – REVISED MARCH 2008

BTD2-BTD0—Batch Time Delay mode. These are the selection bits that specify the delay before a

sample/conversion scan cycle is triggered. When it is set, Batch Time Delay mode uses a set of timers to

automatically trigger a sequence of sample-and-conversion events. The mode works for both TSC-initiated scans

(XYZ or XY) and host-initiated scans (XYZ or XY).

A TSC-initiated scan (XYZ or XY) can be configured by setting the PSM bit in CFR0 to '1' and C[3:0] in Control

Byte 1 to '0000' or '0001'. In the case of a TSC-initiated scan (XYZ or XY), the sequence begins with the TSC

responding to a pen touch. After the first processed sample set completes during the batch delay, the scan

enters a wait mode until the end of the batch delay is reached. If a pen touch is still detected at that moment, the

scan continues to process the next sample set, and the batch delay is resumed. The throughput of the processed

sample sets (shown in Table 21 as sample sets per second, or SSPS) is regulated by the selected batch delay

during the time of the detected pen touch. A TSC-initiated scan (XYZ or XY) can be configured by setting the

PSM bit in CFR0 to '1' and C[3:0] in Control Byte 1 to '0000' or '0001'. Note that the throughput of the processed

sample set also depends on the settings of stabilization, precharge, and sense times, and the total number of

samples to be processed per coordinates. If the accrual time of these factors exceeds the batch delay time, the

accrual time dominates. Batch delay time starts when the pen touch initiates the scan function that converts

coordinates.

A host-initiated scan (XYZ or XY) can be configured by setting the PSM bit in CFR0 to '0' and C[3:0] in Control

Byte 1 to '0000' or '0001'. For the host-initiated scan (XYZ or XY), the host must set TSC internal register C[3:0]

in Control Byte 1 to '0000' or '0001' initially after a pen touch is detected; see Conversion Controlled by TSC2004

Initiated by Host (TSMode 2), in the Theory of Operation section. After the scan (XYZ or XY) is engaged, the

throughput of the processed sample sets is regulated by the selected batch delay timer, as long as the initial

detected touch is not interrupted.

Table 21. Touch Screen Throughput and Batch Selection Bits

BATCH DELAY SELECTION

THROUGHPUT FOR TSC-INITIATED

DELAY TIME

OR HOST-INITIATED SCAN, XYZ OR XY

BTD2

BTD1

BTD0

(ms)

(SSPS)

Normal operation throughput depends on settings.

1000

500

250

100

For example, if stabilization time, precharge time, and sense time are selected as 100

µs, 84µs, and 96µs,

respectively, and the batch delay time is 2ms, then the scan function enters wait mode after the first processed

sample set until the 2ms of batch delay time is reached. When the scan function starts to process the second

sample set (if the screen is still touched), the batch delay restarts at 2ms (in this example). This procedure

remains regulated by 2ms until the pen touch is not detected or the scan function is stopped by a stop bit or any

reset form.

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