PIC16F688-E/P Microchip Technology, PIC16F688-E/P Datasheet - Page 174

• Manufacturer Part Number: PIC16F688-E/P
• Description: IC MCU PIC FLASH 4KX14 14DIP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F688-E/P

• Program Memory Type: FLASH
• Program Memory Size: 7KB (4K x 14)
• Package / Case: 14-DIP (0.300", 7.62mm)
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: UART/USART
• Peripherals: Brown-out Detect/Reset, POR, WDT
• Number Of I /o: 12
• Eeprom Size: 256 x 8
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Interface Type: SCI/USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 12
• Number Of Timers: 2
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 125 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, DM163014, DM164120-4
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 8-ch x 10-bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AC162066 - HEADER INTRFC MPLAB ICD2 20PINAC162061 - HEADER INTRFC MPLAB ICD2 20PINDM163029 - BOARD PICDEM FOR MECHATRONICSAC162056 - HEADER INTERFACE ICD2 16F688ACICE0207 - MPLABICE 14P 300 MIL ADAPTER
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PICmicro MID-RANGE MCU FAMILY
11.5
11.5.1
11.5.2
DS31011A-page 11-6
Note 1: Delay from clock input change to Timer0 increment is 3Tosc to 7Tosc. (Duration of Q = Tosc).
2: External clock if no prescaler selected, Prescaler output otherwise.
3: The arrows indicate the points in time where sampling occurs.
External Clock Synchronization
TMR0 Increment Delay
Using Timer0 with an External Clock
External Clock/Prescaler
Output after sampling
External Clock Input or
Prescaler output
Therefore, the error in measuring the interval between two edges on Timer0 input = 4Tosc max.
Increment Timer0 (Q4)
When an external clock input is used for Timer0, it must meet certain requirements as detailed
in
can be synchronized with the internal phase clock (T
incrementing of Timer0 after synchronization.
When no prescaler is used, the external clock input is the same as the prescaler output. The syn-
chronization of T0CKI with the internal phase clocks is accomplished by sampling the prescaler
output on the Q2 and Q4 cycles of the internal phase clocks
essary for T0CKI to be high for at least 2Tosc (and a small RC delay of 20 ns) and low for at least
2Tosc (and a small RC delay of 20 ns). Refer to
ification of the desired device.
When a prescaler is used, the external clock input is divided by an asynchronous ripple-counter
type prescaler so that the prescaler output is symmetrical. For the external clock to meet the
sampling requirement, the ripple-counter must be taken into account. Therefore, it is necessary
for T0CKI to have a period of at least 4Tosc (and a small RC delay of 40 ns) divided by the pres-
caler value. The only requirement on T0CKI high and low time is that they do not violate the min-
imum pulse width requirement of 10 ns. Refer to
specification of the desired device.
Since the prescaler output is synchronized with the internal clocks, there is a small delay from
the time the external clock edge occurs to the time the Timer0 module is actually incremented.
Figure 11-5
Figure 11-5: Timer0 Timing with External Clock
11.5.1 “External Clock Synchronization.”
(2)
Timer0
shows the delay from the external clock edge to the timer incrementing.
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
(3)
(1)
T0
parameters
These requirements ensure the external clock
parameters
OSC
T0 + 1
). Also, there is a delay in the actual
40,
(Figure
41
40,
and
1997 Microchip Technology Inc.
41
11-5). Therefore, it is nec-
42
and
in the electrical spec-
T0 + 2
42
Small pulse
misses sampling
in the electrical