Comparators; Comparator Operation; Comparator Registers - Holtek HT67F2350 Manual

HT67F2350/HT67F2360
HT67F2370/HT67F2390
Advanced A/D Flash MCU with LCD & EEPROM

Comparators

Two independent analog conparators are contained in these devices. The comparator functions offer
flexibility via their register controlled features such as power-down, polarity select, response time,
etc. In sharing their pins with normal I/O pins the comparators do not waste precious I/O pins if the
comparator functions are otherwise unused.
Cn+
Cn−
Pin-shared
Selection

Comparator Operation

The devices contain two comparator functions which are used to compare two analog voltages
and provide an output based on their difference. Full control over the two internal comparators is
provided via the control register, CP0C and CP1C, one assigned to each comparator. The comparator
output is recorded via a bit in the control register, but can also be transferred out onto a shared I/O
pin. Additional comparator functions include output polarity, response time and power down control.
Any pull-high resistors connected to the shared comparator input pins will
disconnected when the comparator is enabled. As the comparator inputs approach their switching
level, some spurious output signals may be generated on the comparator output due to the slow
rising or falling nature of the input signals. This can be minimised by the hysteresis function which
will apply a small amount of positive feedback to the comparator. When the comparator operates
in the normal mode, the hysteresis function will automatically be enabled. However, the hysteresis
function will be disabled when the comparator operates in the input offset calibration mode.
Ideally the comparator should switch at the point where the positive and negative inputs signals are
at the same voltage level. However, unavoidable input offsets introduce some uncertainties here. The
offset calibration function, if executed, will minimise the switching offset value. The comparator
also provides the output response time select function using the CNVTn1~CNVTn0 bits in the
CPnC register.

Comparator Registers

There are four registers for overall comparator operation, two registers, CPnC and CPnVOS, for
each comparator. As corresponding bits in these registers have identical functions, the following
register table applies to the registers.
Register
Name
7
CPnC —
CPnVOS —
Rev. 1.60
CnPOL CnOUT
+
−
CnEN
Comparators – n=0~1
Bit
6 5 4
CnEN CnPOL CnOUT
CnOFM CnRSP CnOF4
Comparator Registers List – n=0~1
219
CPnINT
One
CnX
Shot
Pin-shared
Selection
be automatically
3 2 1
CNVTn1 CNVTn0 —
CnOF3 CnOF2 CnOF1
May 16, 2019
0
—
CnOF0