NXP Semiconductors LPC84x, User Manual

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Chapter 28: LPC84x Analog comparator
select the comparator output as one of the ADC trigger inputs through the ADC trigger
select register (see
Table 444 “A/D Conversion Sequence A Control Register
(SEQA_CTRL, address 0x4001 C008) bit description” and Table 445 “A/D Conversion
Sequence A Control Register (SEQA_CTRL, address 0x4001 C008) bit description” .
28.4 Pin description
The analog comparator reference voltage, the inputs, and the output are assigned to
external pins through the switch matrix. You can assign the analog comparator output to
any pin on the package that is not a supply or ground pin. The comparator inputs and the
reference voltage are fixed-pin functions that must be enabled through the switch matrix
and can only be assigned to special pins on the package.
See Section 10.3.1 “Connect an internal signal to a package pin” to assign the analog
comparator output to any pin on the LPC84x package.
28.5 General description
The analog comparator can compare voltage levels on external pins and internal voltages.
The comparator has seven inputs multiplexed separately to its positive and negative
inputs. The multiplexers are controlled by the comparator register CTL (see
Figure 63 and
Table 464 ).
Input 0 of the multiplexer is the programmable voltage ladder output.
Inputs 1 to 5 connect the external inputs ACMP_I[5:1].
Input 6 of the multiplexer connects the internal reference voltage input.
Input 7 of the multiplexer connects the DACOUT0.
Table 462. Analog comparator pin description
Function Type Pin Description SWM register Reference
ACMP_I1 I PIO0_0 Comparator input 1 PINENABLE0 Table 195
ACMP_I2 I PIO0_1 Comparator input 2 PINENABLE0 Table 195
ACMP_I3 I PIO0_14 Comparator input 3 PINENABLE0 Table 195
ACMP_I4 I PIO0_23 Comparator input 4 PINENABLE0 Table 195
ACMP_I5 I PIO0_30 Comparator input 5 PINENABLE0 Table 195
ACMP_O O any Comparator output PINASSIGN11 Table 191
VDDCMP I PIO0_6 External reference voltage source for
32-stage Voltage Ladder. PINENABLE0 Table 195