PIC16F74-I/P Microchip Technology, PIC16F74-I/P Datasheet - Page 47

• Manufacturer Part Number: PIC16F74-I/P
• Description: IC MCU FLASH 4KX14 A/D 40DIP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F74-I/P

• Core Size: 8-Bit
• Program Memory Size: 7KB (4K x 14)
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Core Processor: PIC
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Number Of I /o: 33
• Program Memory Type: FLASH
• Ram Size: 192 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 5.5 V
• Data Converters: A/D 8x8b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• Controller Family/series: PIC16F
• No. Of I/o's: 33
• Ram Memory Size: 192Byte
• Cpu Speed: 20MHz
• No. Of Timers: 3
• Package: 40PDIP
• Device Core: PIC
• Family Name: PIC16
• Maximum Speed: 20 MHz
• Operating Supply Voltage: 5 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 33
• Interface Type: I2C/SPI/USART
• On-chip Adc: 8-chx8-bit
• Number Of Timers: 3
• Processor Series: PIC16F
• Core: PIC
• Data Ram Size: 192 B
• Maximum Clock Frequency: 20 MHz
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: ICE2000, DM163022
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 444-1001 - DEMO BOARD FOR PICMICRO MCU
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

5.3
There is only one prescaler available on the microcon-
troller; it is shared exclusively between the Timer0
module and the Watchdog Timer. The usage of the
prescaler is also mutually exclusive: that is, a prescaler
assignment for the 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.
Examples of code for assigning the prescaler assign-
ment are shown in Example 5-1 and Example 5-2.
Note that when the prescaler is being assigned to the
WDT with ratios other than 1:1, lines 2 and 3 (high-
lighted) are optional. If a prescale ratio of 1:1 is to used,
EXAMPLE 5-1:
EXAMPLE 5-2:
TABLE 5-1:
 2002 Microchip Technology Inc.
Address
01h,101h
0Bh,8Bh,
10Bh,18Bh
81h,181h
Legend: x = unknown, u = unchanged, - = unimplemented locations read as ’0’. Shaded cells are not used by Timer0.
1)
2)
3)
4)
5)
6)
7)
8)
9)
10) MOVLW
11) MOVWF
12) BCF
CLRWDT
BSF
MOVLW
MOVWF
BCF
BSF
MOVLW
MOVWF
BCF
CLRF
BSF
MOVLW
MOVWF
CLRWDT
Prescaler
STATUS, RP0
b’xxxx0xxx’
OPTION_REG
STATUS, RP0
TMR0
INTCON
OPTION_REG RBPU INTEDG
STATUS, RP0
b’xx0x0xxx’
OPTION_REG
STATUS, RP0
TMR0
STATUS, RP1
b’xxxx1xxx’
OPTION_REG
b’xxxx1xxx’
OPTION_REG
STATUS, RP0
Name
REGISTERS ASSOCIATED WITH TIMER0
CHANGING THE PRESCALER ASSIGNMENT FROM TIMER0 TO WDT
CHANGING THE PRESCALER ASSIGNMENT FROM WDT TO TIMER0
Timer0 Module Register
Bit 7
; Clear WDT and prescaler
; Bank1
; Select TMR0, new prescale
; value and clock source
; Bank0
GIE
; Bank1
; Select clock source and prescale value of
; other than 1:1
; Bank0
; Clear TMR0 and prescaler
; Bank1
; Select WDT, do not change prescale value
; Clears WDT and prescaler
; Select new prescale value and WDT
; Bank0
PEIE
Bit 6
TMR0IE
T0CS
Bit 5
T0SE
INTE
Bit 4
RBIE
Bit 3
PSA
however, these lines must be used to set a temporary
value. The final 1:1 value is then set in lines 10 and 11
(highlighted). (Line numbers are included in the exam-
ple for illustrative purposes only, and are not part of the
actual code.)
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.
Note:
TMR0IF
Bit 2
PS2
Writing to TMR0 when the prescaler is
assigned to Timer0, will clear the prescaler
count but will not change the prescaler
assignment.
Bit 1
INTF
PS1
Bit 0
RBIF
PS0
PIC16F7X
xxxx xxxx uuuu uuuu
0000 000x 0000 000u
1111 1111 1111 1111
Value on:
POR,
BOR
DS30325B-page 45
Value on
RESETS
all other