PIC16F877-04E/PT Microchip Technology, PIC16F877-04E/PT Datasheet - Page 434

• Manufacturer Part Number: PIC16F877-04E/PT
• Description: IC MCU FLASH 8KX14 EE 44TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F877-04E/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 4MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 33
• Program Memory Size: 14KB (8K x 14)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 368 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 44-TQFP, 44-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: PIC16F87704E/PT

PICmicro MID-RANGE MCU FAMILY
23.7.1
DS31023A-page 23-12
Faster Conversion - Lower Resolution Trade-off
Not all applications require a result with 10-bits of resolution, but may instead require a faster
conversion time. The A/D module allows users to make the trade-off of conversion speed to res-
olution. Regardless of the resolution required, the acquisition time is the same. To speed up the
conversion, the clock source of the A/D module may be switched so that the T
the minimum specified time (see the applicable electrical specification). Once the T
lates the minimum specified time, all the following A/D result bits are not valid (see A/D Conver-
sion Timing in the Electrical Specifications section). The clock sources may only be switched
between the three oscillator versions (cannot be switched from/to RC). The equation to deter-
mine the time before the oscillator can be switched is as follows:
Since the T
ware loop, etc.) to determine when the A/D oscillator may be changed.
comparison of time required for a conversion with 4-bits of resolution, versus the 10-bit resolution
conversion. The example is for devices operating at 20 MHz (The A/D clock is programmed for
32T
The 2T
values.
Example 23-4:
Note 1: A minimum T
T
T
2T
AD
OSC
Conversion time
Where: N
OSC
AD
2: If the full 8-bit conversion is required, the A/D clock source should not be changed.
OSC
+ N • T
), and assumes that immediately after 6T
AD
violates the minimum T
AD
is based from the device oscillator, the user must use some method (a timer, soft-
+ (11 - N)(2T
4-bit vs. 8-bit Conversion Times
= T
= number of bits of resolution required.
AD
time of 1.6 s is required.
AD
Preliminary
+ N • T
OSC
)
AD
AD
time since the last 4 bits will not be converted to correct
+ (11 - N)(2T
(MHz)
Freq.
20
20
20
AD
, the A/D clock is programmed for 2T
(1)
OSC
)
1.6 s
8.7 s
50 ns
4-bit
1997 Microchip Technology Inc.
Resolution
Example 23-4
AD
17.6 s
time violates
10-bit
1.6 s
50 ns
AD
time vio-
shows a
OSC
.