Adc data register – adcl and adch – Rainbow Electronics AT90LS8535 User Manual
Page 73
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AT90S/LS8535
1041H–11/01
ADSC will read as one as long as a conversion is in progress. When the conversion is
complete, it returns to zero. When a extended conversion precedes a real conversion,
ADSC will stay high until the real conversion completes. Writing a “0” to this bit has no
effect.
• Bit 5 – ADFR: ADC Free Running Select
When this bit is set (one), the ADC operates in Free Running Mode. In this mode, the
ADC samples and updates the data registers continuously. Clearing this bit (zero) will
terminate Free Running Mode.
• Bit 4 – ADIF: ADC Interrupt Flag
This bit is set (one) when an ADC conversion completes and the data registers are
updated. The ADC Conversion Complete interrupt is executed if the ADIE bit and the I-
bit in SREG are set (one). ADIF is cleared by hardware when executing the correspond-
ing interrupt handling vector. Alternatively, ADIF is cleared by writing a logical “1” to the
flag. Beware that if doing a read-modify-write on ADCSR, a pending interrupt can be dis-
abled. This also applies if the SBI and CBI instructions are used.
• Bit 3 – ADIE: ADC Interrupt Enable
When this bit is set (one) and the I-bit in SREG is set (one), the ADC Conversion Com-
plete interrupt is activated.
• Bits 2..0 – ADPS2..ADPS0: ADC Prescaler Select Bits
These bits determine the division factor between the XTAL frequency and the input
clock to the ADC.
ADC Data Register – ADCL
AND ADCH
When an ADC conversion is complete, the result is found in these two registers.
When ADCL is read, the ADC Data Register is not updated until ADCH is read. Conse-
quently, it is essential that both registers are read and that ADCL is read before ADCH.
Table 28. ADC Prescaler Selections
ADPS2
ADPS1
ADPS0
Division Factor
0
0
0
2
0
0
1
2
0
1
0
4
0
1
1
8
1
0
0
16
1
0
1
32
1
1
0
64
1
1
1
128
Bit
15
14
13
12
11
10
9
8
$05 ($25)
–
–
–
–
–
–
ADC9
ADC8
ADCH
$04 ($24)
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
ADCL
7
6
5
4
3
2
1
0
Read/Write
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0