PIC16F946T-I/PT Microchip Technology, PIC16F946T-I/PT Datasheet - Page 164

• Manufacturer Part Number: PIC16F946T-I/PT
• Description: Microcontroller
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F946T-I/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 14KB (8K x 14)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 336 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TFQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: MA160011 - DAUGHTER BOARD PICDEM LCD 16F91X
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

PIC16F946
13.1.2
To read a data memory location, the user must write the
address to the EEADRL register, clear the EEPGD
control bit (EECON1<7>), and then set control bit RD
(EECON1<0>). The data is available in the very next
cycle, in the EEDATL register; therefore, it can be read
in the next instruction. EEDATL will hold this value until
another read or until it is written to by the user (during
a write operation).
EXAMPLE 13-1:
13.1.3
To write an EEPROM data location, the user must first
write the address to the EEADRL register and the data
to the EEDATL register. Then the user must follow a
specific sequence to initiate the write for each byte.
The write will not initiate if the sequence described below
is not followed exactly (write 55h to EECON2, write AAh
to EECON2, then set WR bit) for each byte. Interrupts
should be disabled during this code segment.
Additionally, the WREN bit in EECON1 must be set to
enable write. This mechanism prevents accidental
writes to data EEPROM due to errant (unexpected)
code execution (i.e., lost programs). The user should
keep the WREN bit clear at all times, except when
updating EEPROM. The WREN bit is not cleared
by hardware.
After a write sequence has been initiated, clearing the
WREN bit will not affect this write cycle. The WR bit will
be inhibited from being set unless the WREN bit is set.
At the completion of the write cycle, the WR bit is
cleared in hardware and the EE Write Complete
Interrupt Flag bit (EEIF) is set. The user can either
enable this interrupt or poll this bit. EEIF must be
cleared by software.
DS41265A-page 162
BSF
BCF
MOVF
MOVWF
BSF
BCF
BSF
BCF
MOVF
READING THE DATA EEPROM
MEMORY
WRITING TO THE DATA EEPROM
MEMORY
STATUS,RP1
STATUS,RP0
DATA_EE_ADDR,W ; Data Memory
EEADR
STATUS,RP0
EECON1,EEPGD
EECON1,RD
STATUS,RP0
EEDATA,W
DATA EEPROM READ
;
; Bank 2
; Address to read
; Bank 3
; Point to Data
; memory
; EE Read
; Bank 2
; W = EEDATA
Preliminary
The steps to write to EEPROM data memory are:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10. At the completion of the write cycle, the WR bit
EXAMPLE 13-2:
If step 10 is not implemented, check the WR bit
to see if a write is in progress.
Write the address to EEADR. Make sure that the
address is not larger than the memory size of
the device.
Write the 8-bit data value to be programmed in
the EEDATA register.
Clear the EEPGD bit to point to EEPROM data
memory.
Set the WREN bit to enable program operations.
Disable interrupts (if enabled).
Execute the special five instruction sequence:
Enable interrupts (if using interrupts).
Clear the WREN bit to disable program
operations.
is cleared and the EEIF interrupt flag bit is set.
(EEIF must be cleared by firmware.) If step 1 is
not implemented, then firmware should check
for EEIF to be set, or WR to clear, to indicate the
end of the program cycle.
• Write 55h to EECON2 in two steps (first to W,
• Write AAh to EECON2 in two steps (first to
• Set the WR bit
BSF
BSF
BTFSC EECON1,WR
GOTO
BCF
MOVF
MOVWF EEADR
MOVF
MOVWF EEDATA
BSF
BCF
BSF
BCF
MOVLW 55h
MOVWF EECON2
MOVLW AAh
MOVWF EECON2
BSF
BSF
BCF
then to EECON2)
W, then to EECON2)
STATUS,RP1
STATUS,RP0
$-1
STATUS,RP0
DATA_EE_ADDR,W;Data Memory
DATA_EE_DATA,W;Data Memory Value
STATUS,RP0
EECON1,EEPGD ;Point to DATA
EECON1,WREN ;Enable writes
INTCON,GIE
EECON1,WR
INTCON,GIE
EECON1,WREN ;Disable writes
DATA EEPROM WRITE
© 2005 Microchip Technology Inc.
;
;Wait for write
;to complete
;Bank 2
;Address to write
;to write
;Bank 3
;memory
;Disable INTs.
;
;Write 55h
;
;Write AAh
;Set WR bit to
;begin write
;Enable INTs.