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Programmer’s Reference
4-34
Copyright © ARM Limited 2000. All rights reserved.
4.7
Programming the touch screen controller
The SA-1100 and ADS7843 communicate using the SPI bus. The host sends control
bytes to set operating parameters and to request X and Y co-ordinate data. The
ADS7843 responds by returning coordinate data.
4.7.1
Touch screen controller control byte
The ADS7843 carries out acquisition on the requested channel as soon as it has received
enough information contained in the control byte, reducing the delay before it returns
the acquired data. Table 4-23 defines the bit assignment in a control byte from the
SA-1100.
Table 4-23 Control byte
Bit
Name
Function
7
S
Start bit, always 1.
6:4
A2:0
Channel select bits:
001 = X
101 =Y
010 = No function on The P1100
110 = No function on The P1100
3
MODE
Selects 12-bit or 8-bit conversion:
0 = 12 bits
1 = 8 bits.
2
SER/DFR
Selects single-ended or differential mode:
0 = Differential
1 = Single-ended
1:0
PD1:0
Power down mode:
00 = Power down between transaction. No delays are
required when the device returns to full operation and the
first conversion is valid. PENIRQ is enabled
01 = Power down between conversions. PENIRQ is disabled.
10 = Reserved.
11 = Device is always powered.
Summary of Contents for Prospector P1100
Page 1: ...ARM DUI 0122A Prospector P1100 User Guide ...
Page 4: ...iv Copyright ARM Limited 2000 All rights reserved ARM DUI 0122A ...
Page 86: ...Hardware Description 3 54 Copyright ARM Limited 2000 All rights reserved ARM DUI 0122A ...
Page 140: ...Connector reference A 18 Copyright ARM Limited 2000 All rights reserved ARM DUI 0122A ...