C167CS datasheet(365/517 Pages) INFINEON

365 / 517 page

C167CS

Derivatives

The Analog/Digital Converter

User’s Manual

18-8

V2.0, 2000-07

Wait for ADDAT Read Mode

If in default mode of the ADC a previous conversion result has not been read out of

ADDAT is lost because it is overwritten by the new value, and the A/D overrun error

interrupt request flag ADEIR will be set.

In order to avoid error interrupts and the loss of conversion results especially when using

continuous conversion modes, the ADC can be switched to “Wait for ADDAT Read

Mode” by setting bit ADWR in register ADCON.

If the value in ADDAT has not been read by the time the current conversion is complete,

the new result is stored in a temporary buffer and the next conversion is suspended

(ADST and ADBSY will remain set in the meantime, but no end-of-conversion interrupt

will be generated). After reading the previous value from ADDAT the temporary buffer is

copied into ADDAT (generating an ADCIR interrupt) and the suspended conversion is

started. This mechanism applies to both single and continuous conversion modes.

Note: While in standard mode continuous conversions are executed at a fixed rate

(determined by the conversion time), in “Wait for ADDAT Read Mode” there may

be delays due to suspended conversions. However, this only affects the

conversions, if the CPU (or PEC) cannot keep track with the conversion rate.

Figure 18-4

Wait for Read Mode Example

Result of Channel:

Read of ADDAT;

# x

# 2

# 3

# 1

MCA01970

# 0

Request

Generate Interrupt

Temp-Latch Full

ADDAT Full

Write ADDAT

# x

of Channel..

Conversion

# 3

# 2

# 3

Temp-Latch

Hold Result in

# 2

# 1

wait

# 1

# 0

# 3

# 0

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