PIC16F628A-I/P Microchip Technology Inc., PIC16F628A-I/P Datasheet - Page 61

• Manufacturer Part Number: PIC16F628A-I/P
• Description: 18 PIN, 3.5 KB FLASH, 224 RAM, 16 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F628A-I/P

• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 128 Bytes
• Input Output: 16
• Interface: USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 18-pin PDIP
• Programmable Memory: 3.5K Bytes
• Ram Size: 224 Bytes
• Speed: 20 MHz
• Timers: 2-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

10.0
The Voltage Reference is a 16-tap resistor ladder
network that provides a selectable voltage reference.
The resistor ladder is segmented to provide two ranges
of V
conserve power when the reference is not being used.
The VRCON register controls the operation of the
reference as shown in Figure 10-1. The block diagram
is given in Figure 10-1.
REGISTER 10-1:
FIGURE 10-1:
 2003 Microchip Technology Inc.
REF
Note
V
REN
VOLTAGE REFERENCE
MODULE
values and has a power-down function to
bit 7
bit 6
bit 5
bit 4
bit 3-0
1:
R is defined in Table 17-2.
Vref
VRCON REGISTER (ADDRESS: 9Fh)
VOLTAGE REFERENCE BLOCK DIAGRAM
bit 7
V
1 = V
0 = V
V
1 = V
0 = V
V
1 = Low Range
0 = High Range
Unimplemented: Read as '0'
V
When V
When V
Legend:
R = Readable bit
-n = Value at POR
R
REN
ROE
RR
R/W-0
V
V
<3:0>: V
DD
REN
: V
: V
: V
REF
REF
REF
REF
REF
RR
RR
REF
REF
8R
circuit powered on
circuit powered down, no I
is output on RA2 pin
is disconnected from RA2 pin
Range selection
= 1: V
= 0: V
REF
Enable
Output Enable
R/W-0
V
value selection 0 ≤ V
ROE
REF
REF
R
= (V
= 1/4 * V
R/W-0
R
V
<3:0>/ 24) * V
R
Preliminary
RR
W = Writable bit
’1’ = Bit is set
DD
16 Stages
+ (V
16-1 Analog Mux
DD
R
R
U-0
[3:0] ≤ 15
<3:0>/ 32) * V
—
drain
10.1
The Voltage Reference can output 16 distinct voltage
levels for each range.
The equations used to calculate the output of the
Voltage Reference are as follows:
The setting time of the Voltage Reference must be
considered when changing the V
(Table 17-2). Example 10-1 shows an example of how
to configure the Voltage Reference for an output
voltage of 1.25V with V
DD
if V
if V
V
R
DD
RR
RR
Configuring the Voltage Reference
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared
R/W-0
= 1: V
= 0: V
V
DD
R3
R
REF
REF
= (V
V
= (V
SS
DD
R/W-0
V
8R
R
PIC16F62X
= 5.0V.
R2
<3:0>/24) x V
DD
Vr3
Vr0
x 1/4) + (V
x = Bit is unknown
V
REF
SS
(From VRCON<3:0>)
R/W-0
V
DS40300C-page 59
output
R1
DD
Vrr
R
<3:0>/32) x
R/W-0
V
R0
bit 0