PIC16F1847-I/SO Microchip Technology, PIC16F1847-I/SO Datasheet - Page 4

• Manufacturer Part Number: PIC16F1847-I/SO
• Description: 14 KB Flash, 1K Bytes RAM, 32 MHz Int. Osc, 16 I/0, Enhanced Mid Range Core 18 S
• Manufacturer: Microchip Technology

Specifications of PIC16F1847-I/SO

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PIC16(L)F1847
3.3 Oscillator Start-up Timer (OST) bit
EXAMPLE 1:
DS80525B-page 4
In firmware, define default, minimum and maximum auto-baud (SPBRG) values according to the application requirements.
For example, if the application runs at 9600 baud at 16 MHz then, the default SPBRG value would be (assuming 16-bit/
Asynchronous mode) 0x67. The minimum and maximum allowed values can be calculated based on the application. In this
example, a +/-5% tolerance is required, so tolerance is 0x67 * 5% = 0x05.
#define SPBRG_16BIT
const int DEFAULT_BAUD = 0x0067;
const int TOL = 0x05;
const int MIN_BAUD = DEFAULT_BAUD - TOL;
const int MAX_BAUD = DEFAULT_BAUD + TOL;
ABDEN = 1;
while (ABDEN);
if((SPBRG_16BIT > MAX_BAUD)||(SPBRG_16BIT < MIN_BAUD))
{
}
•
•
•
•
•
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• MCLR Reset
• Wake from Sleep
During the Two-Speed Start-up sequence, the
OST is enabled to count 1024 clock cycles. After
the count is reached, the OSTS bit is set, the sys-
tem clock is held low until the next falling edge of
the external crystal (LP, XT or HS mode), before
switching to the external clock source.
When an external oscillator is configured as the
primary clock and Fail-Safe Clock mode is enabled
(FCMEN = 1), any of the following conditions will
result in the Oscillator Start-up Timer (OST) failing
to restart:
• Clock change from INTOSC to Primary Clock
This anomaly will manifest itself as a clock failure
condition for external oscillators which take longer
than the clock failure time-out period to start.
Work around
None.
Affected Silicon Revisions
SPBRG_16BIT = DEFAULT_BAUD);
A2
X
METHOD 1 – EUSART AUTO-BAUD DETECT WORK AROUND
*((*int)&SPBRG;
// if in spec, continue using the
// Auto-Baud value in SPBRG
4. Module: Enhanced Universal
4.1 Auto-Baud Detect
// define location for 16-bit SPBRG value
// Default Auto-Baud value
// Baud Rate % tolerance
// Minimum Auto-Baud Limit
// Maximum Auto-Baud Limit
// Start Auto-Baud
// Wait until Auto-Baud completes
// Compare if value is within limits
// if out of spec, use DEFAULT_BAUD
When using automatic baud detection (ABDEN),
on occasion, an incorrect count value can be
stored at the end of auto-baud detection in the
SPBRGH:SPBRGL
SPBRG value may be off by several counts. This
condition happens sporadically when the device
clock frequency drifts to a frequency where the
SPBRG value oscillates between two different
values. The issue is present regardless of the
baud rate Configuration bit settings.
Work around
When using auto-baud, it is a good practice to
always verify the obtained value of SPBRG, to
ensure
specifications. Two recommended methods are
shown below.
For
Technical Brief TB3069, “Use of Auto-Baud for
Reception of LIN Serial Communications Devices:
Mid-Range and Enhanced Mid-Range”.
additional
it
Synchronous Asynchronous
Receiver (EUSART)
remains
 2011-2012 Microchip Technology Inc.
auto-baud
(SPBRG)
within
information,
the
registers.
application
The
see