PIC16F874A-I/PT Microchip Technology, PIC16F874A-I/PT Datasheet - Page 56

• Manufacturer Part Number: PIC16F874A-I/PT
• Description: IC MCU FLASH 4K 20MHZ 44-TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F874A-I/PT

• Program Memory Type: FLASH
• Program Memory Size: 7KB (4K x 14)
• Package / Case: 44-TQFP, 44-VQFP
• 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
• Eeprom Size: 128 x 8
• Ram Size: 192 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 192 B
• Interface Type: I2C/SPI/USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 33
• Number Of Timers: 3
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, DM163022, DV164120
• 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: XLT44PT3 - SOCKET TRAN ICE 44MQFP/TQFPAC164305 - MODULE SKT FOR PM3 44TQFP444-1001 - DEMO BOARD FOR PICMICRO MCUAC164020 - MODULE SKT PROMATEII 44TQFP
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PIC16F87XA
5.2
When no prescaler is used, the external clock input is
the same as the prescaler output. The synchronization
of T0CKI with the internal phase clocks is accom-
plished by sampling the prescaler output on the Q2 and
Q4 cycles of the internal phase clocks. Therefore, it is
necessary for T0CKI to be high for at least 2 T
a small RC delay of 20 ns) and low for at least 2 T
(and a small RC delay of 20 ns). Refer to the electrical
specification of the desired device.
5.3
There is only one prescaler available which is mutually
exclusively shared between the Timer0 module and the
Watchdog Timer. A prescaler assignment for the
REGISTER 5-1:
DS39582B-page 54
Using Timer0 with an External
Clock
Prescaler
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
OPTION_REG REGISTER
bit 7
RBPU
INTEDG
T0CS: TMR0 Clock Source Select bit
1 = Transition on T0CKI pin
0 = Internal instruction cycle clock (CLKO)
T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on T0CKI pin
0 = Increment on low-to-high transition on T0CKI pin
PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
PS2:PS0: Prescaler Rate Select bits
Legend:
R = Readable bit
- n = Value at POR
Bit Value TMR0 Rate WDT Rate
Note:
R/W-1
RBPU
000
001
010
011
100
101
110
111
To avoid an unintended device Reset, the instruction sequence shown in the
PICmicro
cuted when changing the prescaler assignment from Timer0 to the WDT. This
sequence must be followed even if the WDT is disabled.
INTEDG
R/W-1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
®
OSC
Mid-Range MCU Family Reference Manual (DS33023) must be exe-
R/W-1
T0CS
(and
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
OSC
W = Writable bit
‘1’ = Bit is set
R/W-1
T0SE
Timer0 module means that there is no prescaler for the
Watchdog Timer and vice versa. This prescaler is not
readable or writable (see Figure 5-1).
The PSA and PS2:PS0 bits (OPTION_REG<3:0>)
determine the prescaler assignment and prescale ratio.
When assigned to the Timer0 module, all instructions
writing to the TMR0 register (e.g., CLRF 1, MOVWF 1,
BSF 1,x....etc.) will clear the prescaler. When assigned
to WDT, a CLRWDT instruction will clear the prescaler
along with the Watchdog Timer. The prescaler is not
readable or writable.
Note:
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
R/W-1
PSA
Writing to TMR0 when the prescaler is
assigned to Timer0 will clear the prescaler
count, but will not change the prescaler
assignment.
R/W-1
 2003 Microchip Technology Inc.
PS2
x = Bit is unknown
R/W-1
PS1
R/W-1
PS0
bit 0