Renesas 4514 - Manual (Page 61)

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HARDWARE
4513/4514 Group User’s Manual
FUNCTION BLOCK OPERATIONS
Voltage comparator control register Q3 (Note 2) at reset : 0000 2 at RAM back-up : state retained
Q3 3
Q3 2
Q3 1
Q3 0
Voltage comparator (CMP1) invalid
Voltage comparator (CMP1) valid
Voltage comparator (CMP0) invalid
Voltage comparator (CMP0) valid
CMP1- > CMP1+
CMP1- < CMP1+
CMP0- > CMP0+
CMP0- < CMP0+
Voltage comparator (CMP1) control bit
Voltage comparator (CMP0) control bit
CMP1 comparison result store bit
CMP0 comparison result store bit
0
1
0
1
0
1
0
1
Notes 1: “R” represents read enabled, and “W” represents write enabled.
2: Bits 0 and 1 of register Q3 can be only read.
(1) Voltage comparator control register Q3
Register Q3 controls the function of the voltage comparator.
The function of the voltage comparator CMP0 becomes valid by
setting bit 2 of register Q3 to “1,” and becomes invalid by setting bit
2 of register Q3 to ”0.” The comparison result of the voltage com-
parator CMP0 is stored into bit 0 of register Q3.
The function of the voltage comparator CMP1 becomes valid by
setting bit 3 of register Q3 to “1,” and becomes invalid by setting bit
3 of register Q3 to ”0.” The comparison result of the voltage com-
parator CMP1 is stored into bit 1 of register Q3.
( 2 ) O p e r a t i o n d e s c r i p t i o n o f v o l t a g e
comparator
The voltage comparator function becomes valid by setting each
control bit of register Q3 to “1” and compares the voltage of the in-
put pin. The comparison result is stored into each comparison
result store bit of register Q3.
The comparison result is as follows;
• When CMP0- > CMP0+, Q3 0 = “0”
When CMP0- < CMP0+, Q3 0 = “1”
• When CMP1- > CMP1+, Q3 1 = “0”
When CMP1- < CMP1+, Q3 1 = “1”
(3) Precautions
When the voltage comparator is used, note the following;
• Voltage comparator function
When the voltage comparator function is valid with the voltage
comparator control register Q3, it is operating even in the RAM
back-up mode. Accordingly, be careful about such state because
it causes the increase of the operation current in the RAM back-
up mode.
In order to reduce the operation current in the RAM back-up
mode, invalidate (bits 2 and 3 of register Q3 = “0”) the voltage
comparator function by software before the POF instruction is
executed.
Also, while the voltage comparator function is valid, current is al-
ways consumed by voltage comparator. On the system required
for the low-power dissipation, invalidate the voltage comparator
by software when it is unused.
• Register Q3
Bits 0 and 1 of register Q3 can be only read. Note that they can-
not be written.
• Reading the comparison result of voltage comparator
Read the voltage comparator comparison result from register Q3
after the voltage comparator response time (max. 20
µ
s) is
passed from the voltage comparator function becomes valid.
R/W
Table 18 Voltage comparator control register Q3