pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 176

• Manufacturer Part Number: pc87591l
• Description: Lpc Mobile Embedded Controllers
• Manufacturer: National Semiconductor Corporation

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Embedded Controller Modules
See Section 7.4 on page 378 for the values of t
on page 173 for t
Temperature inputs from remote and local diodes are measured by alternating the remote and local diodes in each succes-
sive ADC cycle. If the remote diode measurement is disabled (RDMEASEN is set to 0 in TCHANCTL register or REMDEN
in ADCCNF register is set to 0), the local diode temperature is measured every ADC cycle.
Input Selection Field. Each Voltage Channel has its own programmable, input selection field (SELIN in VCHNxCTL regis-
ter). This field determines which input is measured by the channel during the current ADC cycle. The field also indicates to
which input the data in the channel buffer belongs. This field may be modified after the channel buffer has been read and
the DATVAL bit has been reset.
If the input selection field is not changed, the same input is measured during the next ADC cycle. This gives a sampling rate
of one T
each input, but the period for all scanned inputs is shorter.
Operation Sequence. After the ADC is properly initialized and enabled, one of the following example sequences can be used:
EOCEV-Driven ADC Operation Sequence for All Channels
1. When End-of-Cycle is reached (i.e., after all enabled channel conversions are completed), software can detect the event
2. Read the input number of the temperature channel by reading SELIN in TCHANCTL register.
3. Read the temperature value measured by reading TCHDAT in TCHANDAT register.
4. In preparation for the next measurement, clear DATVAL bit in TCHANCTL register by writing 1 to it.
5. Measure the input number for Voltage Channel 1 by reading SELIN in VCHN1CTL register.
6. Read the number of input measured in Voltage Channel 1 by reading VCHDAT in VCHN1DAT register.
7. In preparation for the next measurement (i.e., to define which input will be measured by Voltage Channel 1 during the
8. For Voltage Channel 2, repeat steps 5 through 7 for the VCHN2CTL and VCHN2DAT registers.
9. For Voltage Channel 3, repeat steps 5 through 7 for the VCHN3CTL and VCHN3DAT registers.
DATVAL-Driven ADC Operation Sequence for One Channel
1. Measure the end of channel by waiting for DATVAL in TCHANCTL or VCHNxCTL register to be set to 1.
2. Measure the input number by reading SELIN in TCHANCTL or VCHNxCTL register.
3. Read the measured data by reading TCHDAT or VCHDAT in TCHANDAT or VCHNxDAT register, respectively.
4. Optional (for voltage channels only): Change the input to be measured during the next ADC cycle: in VCHNxCTL regis-
5. Prepare the temperature or voltage channel to receive new data: in TCHANCTL or VCHNxCTL register, write 1 to
6. In preparation for the next measurement (i.e., to define which input will be measured by the temperature channel or the
Reading Measurement Results
Polling-Driven Operation. Measurement results may be read by polling either EOCEV in ADCSTS register or each of the
four DATVAL bits in TCHANCTL register and three VCHNxCTL registers.
Polling EOCEV uses the sequence listed in “EOCEV-Driven ADC Operation Sequence for All Channels”, above. When
EOCEV is set, all four channels contain valid data and may be read.
Polling DATVAL uses the sequence listed in “DATVAL-Driven ADC Operation Sequence for One Channel”, above. When a
DATVAL bit is set, only its channel contains valid data that may be read. In this case, the EOCEV bit is redundant.
Interrupt-Driven Operation. The ADC may generate an interrupt to the core when any of the valid bits is set (EOCEV in
ADCSTS register or DATVAL in either TCHANCTL or any VCHNxCTL register). The interrupt is generated when the interrupt
enable bit for the respective status bit is set. The software in the interrupt routine should check the status bits as described
above for polling-driven operation to verify which of the DATVAL bits is set.
EOCEV-driven ADC operation sequence for all temperature and voltage channels
DATVAL-driven ADC operation sequence for one temperature or voltage channel
by waiting for EOCEV bit in ADCSTS register to be set to 1.
next ADC cycle), clear DATVAL bit in VCHN1CTL register by writing 1 to it (it may be the same input or, optionally, a different
one).
ter, write a new SELIN value.
DATVAL to clear it.
voltage channel during the next ADC cycle), clear the DATVAL bit by writing 1 to it (it may be the same input or, option-
ally, a different one).
ADC cycle
VC
for the specific input. If this field is changed and a different input is sampled, the sampling rate is lower for
calculation.
(Continued)
TC
, Section 4.11.4 on page 173 for t
176
TD
calculation and Section Section 4.11.3
Revision 1.07