PIC16LC433T-I/SO Microchip Technology, PIC16LC433T-I/SO Datasheet - Page 39

• Manufacturer Part Number: PIC16LC433T-I/SO
• Description: IC MCU CMOS 8BIT 10MHZ 2K 18SOIC
• Manufacturer: Microchip Technology
• Series: PIC® 16Cr

Specifications of PIC16LC433T-I/SO

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 10MHz
• Connectivity: LIN (Local Interconnect Network)
• Peripherals: POR, WDT
• Number Of I /o: 6
• Program Memory Size: 3.5KB (2K x 14)
• Program Memory Type: OTP
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 5.5 V
• Data Converters: A/D 4x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 18-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -

7.2
When an external clock input is used for Timer0, it must
meet certain requirements. The requirements ensure
the external clock can be synchronized with the internal
phase clock (T
incrementing of Timer0 after synchronization.
7.2.1
When no prescaler is used, the external clock input is
used as the clock source. The synchronization 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 (Figure 7-5). There-
fore, it is necessary for T0CKI to be high for at least
2T
least 2T
the electrical specification of the desired device.
FIGURE 7-5:
2001 Microchip Technology Inc.
OSC
Note 1:
(and a small RC delay of 20 ns) and low for at
OSC
2:
3:
Using Timer0 with an External Clock
EXTERNAL CLOCK SYNCHRONIZATION
External Clock Input or
Prescaler Output
External Clock/Prescaler
Output after Sampling
Increment Timer0 (Q4)
(and a small RC delay of 20 ns). Refer to
Delay from clock input change to Timer0 increment is 3T
the interval between two edges on Timer0 input = ±4T
External clock if no prescaler selected; prescaler output otherwise.
The arrows indicate the points in time where sampling occurs.
OSC
TIMER0 TIMING WITH EXTERNAL CLOCK
). Also, there is a delay in the actual
Timer0
(2)
Q1
(3)
Q2
Q3
Advance Information
(1)
Q4
Q1
T0
OSC
Q2
OSC
max.
Q3
to 7T
When a prescaler is used, the external clock input is
divided by the asynchronous ripple-counter type pres-
caler, so that the prescaler output is symmetrical. For
the external clock to meet the sampling requirement,
the ripple-counter must be taken into account. There-
fore, it is necessary for T0CKI to have a period of at
least 4T
the prescaler value. The only requirement on T0CKI
high and low time is that they do not violate the mini-
mum pulse width requirement of 10 ns. Refer to param-
eters 40, 41 and 42 in the electrical specification of the
desired device.
7.2.2
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 mod-
ule is actually incremented. Figure 7-5 shows the delay
from the external clock edge to the timer incrementing.
Q4
OSC
(Duration of Q = T
Q1
OSC
T0 + 1
TMR0 INCREMENT DELAY
Q2
(and a small RC delay of 40 ns), divided by
Q3
OSC
Q4
). Therefore, the error in measuring
Q1
PIC16C433
Q2
T0 + 2
Small pulse
misses sampling
Q3
DS41139A-page 37
Q4