PIC16LC774/PQ Microchip Technology, PIC16LC774/PQ Datasheet - Page 125

• Manufacturer Part Number: PIC16LC774/PQ
• Description: IC MCU OTP 4KX14 A/D PWM 44-MQFP
• Manufacturer: Microchip Technology
• Series: PIC® 16Cr

Specifications of PIC16LC774/PQ

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 33
• Program Memory Size: 7KB (4K x 14)
• Program Memory Type: OTP
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2.5 V ~ 5.5 V
• Data Converters: A/D 10x12b
• Oscillator Type: External
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 44-MQFP, 44-PQFP
• Processor Series: PIC16LC
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Interface Type: I2C, SPI, SSP, UART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 33
• Number Of Timers: 3 bit
• Operating Supply Voltage: 2.5 V to 5.5 V
• Maximum Operating Temperature: + 70 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: ICE2000, DM163022
• Minimum Operating Temperature: 0 C
• On-chip Adc: 10 bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

11.7
An A/D conversion can be started by the “special event
trigger” of the CCP module. This requires that the
CCPnM<3:0> bits be programmed as 1011b and that
the A/D module is enabled (ADON is set). When the
trigger occurs, the GO/DONE bit will be set on Q2 to
start the A/D conversion and the Timer1 counter will
be reset to zero. Timer1 is reset to automatically
repeat the A/D conversion cycle, with minimal software
overhead (moving the ADRESH and ADRESL to the
desired location). The appropriate analog input chan-
nel must be selected before the “special event trigger”
sets the GO/DONE bit (starts a conversion cycle).
If the A/D module is not enabled (ADON is cleared),
then the “special event trigger” will be ignored by the
A/D module, but will still reset the Timer1 counter.
11.8
A device reset forces all registers to their reset state.
This forces the A/D module to be turned off, and any
conversion is aborted. The value that is in the
ADRESH and ADRESL registers are not modified.
The ADRESH and ADRESL registers will contain
unknown data after a Power-on Reset.
1999 Microchip Technology Inc.
Use of the CCP Trigger
Effects of a RESET
Advance Information
11.9
Not all applications require a result with 12-bits of res-
olution, but may instead require a faster conversion
time. The A/D module allows users to make the
trade-off of conversion speed to resolution. Regard-
less of the resolution required, the acquisition time is
the same. To speed up the conversion, the A/D mod-
ule may be halted by clearing the GO/DONE bit after
the desired number of bits in the result have been con-
verted. Once the GO/DONE bit has been cleared, all
of the remaining A/D result bits are ‘0’. The equation
to determine the time before the GO/DONE bit can be
switched is as follows:
Since T
must use some method (a timer, software loop, etc.) to
determine when the A/D GO/DONE bit may be
cleared. Table 11-2 shows a comparison of time
required for a conversion with 4-bits of resolution, ver-
sus the normal 12-bit resolution conversion. The
example is for devices operating at 20 MHz. The A/D
clock is programmed for 32 T
TABLE 11-2
Tosc
T
1T
AD
AD
Where: N = number of bits of resolution required,
and 1T
Conversion time = N•T
= 32 Tosc
+N•T
AD
Faster Conversion - Lower
Resolution Trade-off
AD
AD
is based from the device oscillator, the user
is the amplifier settling time.
4-BIT vs. 12-BIT
CONVERSION TIMES
PIC16C77X
AD
OSC
+ 1T
Freq.
(MHz)
20
20
20
.
AD
DS30275A-page 125
50 ns
1.6 s
8 s
4-bit
Resolution
50 ns
1.6 s
20.8 s
12-bit