D17133CS datasheet(147/289 Pages) NEC

147 / 289 page

CHAPTER 13

PERIPHERAL HARDWARE

132

13.2.2 Functions of Comparator

The comparator has a 4-channel analog input.

Concerning the pins used as analog input of the comparator, set 1 to P0CnIDI (n=0 to 3) at initial setting of the

program (refer to CHAPTER 12 PORTS).

One of analog inputs (Cin0 to Cin3) can be selected by the comparator input channel selection flag (CMPCH1,

CMPCH0 RF: 1CH, bits 1 and 0). One of the 16 types of reference voltages (external: 1, internal: 15) can be selected

by the comparator reference voltage selection flag (CMPVREF0 to CMPVREF3 RF: 1DH).

After setting the comparator start flag to 1 (CMPSTRT RF: 1EH, bit 1), comparison takes 2 instruction execution

cycles in the

µPD17132 and 17P132, and 6 cycles in the µPD17133 and 17P133.

A comparison result is stored to the comparator comparison result flag (CMPRSLT RF: 1EH, bit 0).

Whether the comparator is operating or comparison is completed can be known by reading comparator start flag.

CMPSTRT=1... Comparator is operating (during analog voltage comparison)

CMPSTRT=0... Comparator is stopped (comparison is completed)

When comparing comparator analog voltage (CMPSTRT=1), manipulating comparator input channel selection flag

(CMPCH1 CMPCH0) or comparator reference voltage selection flag (CMPVREF0 to CMPVREF3) is ignored and the

data in these registers remain unchanged. Therefore, changing comparator operation modes are disabled.

CMPSTRT is cleared only when the voltage comparison operation of comparator is completed or when STOP

instruction is executed.

Caution When using the standby function, be sure to wait for the comparator operation to stop before

executing a standby instruction (HALT/STOP). If a STOP or HALT instruction is executed while

the comparator is in operation, the comparator operation is halted. If the internal reference

voltage has been selected at this time, current will keep flowing into the internal resistor ladder,

thus resulting in increased current consumption during standby mode.

Comparator input channel selection register, reference voltage selection register, and comparator operation

control register are shown in the Figures 13-9, 13-10, and 13-11, respectively.

D17133CS Datasheet(PDF) 147 Page - NEC