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EPSON
S1C88409 TECHNICAL MANUAL
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (A/D Converter)
PRAD: A/D converter clock control register
(00FF13HD3)
Controls the clock supply to the A/D converter.
When "1" is written: ON
When "0" is written: OFF
Reading: Invalid
By writing "1" to the PRAD register, the prescaler
outputs the clock selected with the PSAD register
to the A/D converter. However, it is necessary that
the CPU operating clock be set to OSC3.
When "0" is written, the clock is not output to the
A/D converter.
At initial reset, the PRAD register is set to "0"
(OFF).
ADRUN: A/D conversion start trigger
(00FF80HD7)
Starts A/D conversion.
When "1" is written: Start A/D conversion
When "0" is written: Invalid
Reading: Always "0"
By writing "1" to this register, the A/D converter
starts A/D conversion of the channel selected by
the CHS register, and stores the conversion result
to the ADDR register.
VRO: AVREF switch (00FF80HD3)
Turns AVREF on and off.
When "1" is written: On
When "0" is written: Off
Reading: Valid
When "1" is written to the VRO register, AVREF
turns on and when "0" is written turns off.
An I/O port (P30–P37) which is not used for
inputting analog signals can be used to switch the
external AVREF input. Set the I/O port in the
output mode and write "1" to the data register.
Writing "1" to the VRO register in this status turns
the I/O port terminal to low. The signal drives the
external transistor to supply AVREF to the A/D
converter.
At initial reset, the VRO register is set to "0" (OFF).
VRC: AVREF control register (00FF80HD4)
Enables the AVREF to be controlled by the touch
panel controller.
When "1" is written: Enabled
When "0" is written: Disabled
Reading: Valid
Writing "1" to the VRC register sets the touch panel
controller so that it controls the AVREF without the
VRO register.
At initial reset, the VRC register is set to "0"
(disabled).
CHS0–CHS2: Analog input channel selection
register (00FF80HD0–D2)
Selects an analog input channel.
Table 5.18.6.3 Selection of analog input channel
CHS2
1
0
Input channel
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
CHS1
1
0
1
0
CHS0
1
0
1
0
1
0
1
0
At initial reset, the CHS register is set to "0" (AD0).
ADDR0–ADDR9: A/D conversion result
(00FF82H/low-order 2 bits, 00FF81H/high-order 8 bits)
A/D conversion result is stored.
ADDR0 is the LSB and ADDR9 is the MSB.
ADDR0 and ADDR1 are assigned in D0 bit and D1
bit of the address 00FF82H. D2–D7 bits in this
address are always "0" when being read.
At initial reset, data is set to "0".
PAD0, PAD1: A/D converter interrupt priority
register (00FF22HD6, D7)
Sets the priority level of the A/D conversion
completion interrupt.
Table 5.18.6.4 shows the interrupt priority level
which can be set by the PAD register.
Table 5.18.6.4 Interrupt priority level settings
PAD1
1
0
Interrupt priority level
Level 3
Level 2
Level 1
Level 0
PAD0
1
0
1
0
(IRQ3)
(IRQ2)
(IRQ1)
(None)
At initial reset, the PAD register is set to "0" (level 0).