PIC16F1937-I/ML Microchip Technology, PIC16F1937-I/ML Datasheet - Page 15

• Manufacturer Part Number: PIC16F1937-I/ML
• Description: IC PIC MCU FLASH 512KX14 44-QFN
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 16Fr

Specifications of PIC16F1937-I/ML

• Core Size: 8-Bit
• Program Memory Size: 14KB (8K x 14)
• Core Processor: PIC
• Speed: 32MHz
• Connectivity: I²C, LIN, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 36
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 14x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-QFN
• Controller Family/series: PIC16F
• No. Of I/o's: 36
• Eeprom Memory Size: 256Byte
• Ram Memory Size: 512Byte
• Cpu Speed: 32MHz
• No. Of Timers: 5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Fast
Using the BRW instruction combined with RETLW will
assure that all instruction fetches take 4 cycles plus the
initial call. The traditional methods can also run this fast
if the data table is located to prevent problems with the
program memory page size.
If CALL
separated by a page boundary, the PAGESEL is not
required to assure the CALL can reach. This method
never requires the data_table be aligned to any
memory
requirement makes BRW very easy to use. This method
of table access requires 6 or 7 cycles, depending on the
presence of PAGESEL.
Fast
The CALLW instruction can be used to access data
tables anywhere in memory for a fixed 6-cycle time.
CALLW is a new instruction intended to make function
pointers more efficient. In addition to its intended func-
tion, CALLW can also be used to prepare tables of data.
CALLW works by concatenating the value in W with the
value in PCLATH and “calling” the resulting address.
Locating the block of RETLW instructions on a 256-word
boundary (low address byte as zero) allows a CALLW to
retrieve the data. This can be a very fast table lookup.
© 2009 Microchip Technology Inc.
code
data_table
RETLW
RETLW
BRW
RETLW
RETLW
RETLW
RETLW
RETLW
RETLW
RETLW
MOVLW
PAGESEL
CALL
data_table and data_table are not
address.
Tables with
Tables with
‘m’
‘y’
‘ ‘
‘d’
‘a’
‘t’
‘a’
data_index
data_table
data_table
Eliminating
BRW
CALLW
the
alignment
This method takes 6 cycles to retrieve any data.
Example
A complete code example is shown in Appendix B:
“IIR Filter Conversion Example”. In this example, an
IIR function downloaded from the internet is converted
to use the enhanced PIC12/16 features. The resulting
code runs nearly twice as fast.
code
data_table
MOVLP
MOVLW
CALLW
ORG
RETLW
RETLW
RETLW
RETLW
RETLW
RETLW
RETLW
RETLW
HIGH data_table
data_index
0x??00
‘m’
‘y’
‘ ‘
‘d’
‘a’
‘t’
‘a’
0
DS41375A-page 15