CC2430-RTR1-F64Z datasheet(128/234 Pages) TI

128 / 234 page

CC2430

CC2430 PRELIMINARY Data Sheet (rev. 1.03) SWRS036A

Page 128 of 232

the differential inputs consist of the input

pairs AIN0-1, AIN2-3, AIN4-5 and AIN6-7.

In addition to the input pins AIN0-AIN7, the

output of an on-chip temperature sensor

can be selected as an input to the ADC for

temperature measurements.

It is also possible to select a voltage

corresponding to AVDD_SOC/3 as an

ADC input.

This input allows the

implementation of e.g. a battery monitor in

applications where this feature is required.

13.7.2.3 ADC conversion sequences

The ADC will perform a sequence of

conversions, and move the results to

memory (through DMA) without any

interaction from the CPU.

The ADCCON2.SCH register bits are used

to define an ADC conversion sequence,

from the ADC inputs. A conversion

sequence will contain a conversion from

each channel from 0 up to and including

the channel number programmed in

ADCCON2.SCH when ADCCON2.SCH is set

to a value less than 8.

The single-ended inputs AIN0 to AIN7 are

represented by channel numbers 0 to 7 in

ADCCON2.SCH. Channel numbers 8 to 11

represent the differential inputs consisting

of AIN0-AIN1, AIN2-AIN3, AIN4-AIN5 and

AIN6-AIN7. Channel numbers 12 to 15

represent GND, internal voltage reference,

temperature sensor and AVDD_SOC/3,

respectively.

When ADCCON2.SCH is set to a value

between 8 and 12, the sequence will start

at channel 8. For even higher settings,

only single conversions are performed. In

addition to this sequence of conversions,

the ADC can be programmed to perform a

single conversion from any channel as

soon as the sequence has completed.

This is called an extra conversion and is

controlled with the ADCCON3 register.

The conversion sequence can also be

influenced with the ADCCFG register (see

section 13.1.5 on page 72). The eight

analog inputs to the ADC comes from IO

pins,

which

are

not

necessarily

programmed to be analog inputs. If a

channel should normally be part of a

sequence, but the corresponding analog

input is disabled in the ADCCFG, then that

channel will be skipped. For channels 8 to

12, both input pins must be enabled.

13.7.2.4 ADC Operating Modes

This section describes the operating

modes and initialization of conversions.

The ADC has three control registers:

ADCCON1,

ADCCON2 and ADCCON3.

These registers are used to configure the

ADC and to report status.

The ADCCON1.EOC bit is a status bit that

is set high when a conversion ends and

cleared when ADCH is read.

The ADCCON1.ST bit is used to start a

sequence of conversions. A sequence will

start

when

this

bit

set

high,

ADCCON1.STSEL=”11”

and

conversion is currently running. When the

sequence

completed,

this

bit

automatically cleared.

The ADCCON1.STSEL bits select which

event that will start a new sequence of

conversions. The options which can be

selected are rising edge on external pin

P2_0, end of previous sequence, a Timer

channel

compare

event

ADCCON1.ST=’1’.

The ADCCON2 register controls how the

sequence of conversions is performed.

ADCCON2.SREF is used to select the

reference voltage. The reference voltage

should

only

changed

when

conversion is running.

The

ADCCON2.SDIV bits select the

decimation rate (and thereby also the

resolution and time required to complete a

conversion

and

sample

rate).

The

decimation rate should only be changed

when no conversion is running.

The last channel of a sequence is selected

with the ADCCON2.SCH bits.

The

ADCCON3

controls

the

channel number, reference voltage and

decimation rate for the extra conversion.

The extra conversion will take place

immediately after the ADCCON3 register is

updated. The coding of the register bits is

exactly as for ADCCON2.

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