MCP212X Developer’s Daughter Board User’s Guide
DS51571B-page 32
©
2006 Microchip Technology Inc.
The crystal frequency of the PICDEM™ Demo Board determines the error rates for the
EUSART baud rates, as well as the 16XCLK generation (for the MCP2122). So for the
PICDEM™ HPC Explorer Demo Board, the default crystal is 10 MHz (does have a 4x
PLL). Therefore, the 16XCLK frequency for 115200 baud has an error outside usable
limits for IrDA
®
standard communication for both 10 MHz and 40 MHz operation (see
Table D-1). The demo will be limited to 9600 baud. Table D-2 shows the SPBRG values
for the EUSART at the same crystal frequencies.
TABLE D-1:
PR VALUES FOR PWM
(1)
TABLE D-2:
SPBRG VALUES FOR EUSART
(1)
Desired
Baud Rate
16XCLK
@ 40 MHz
(2)
@ 20 MHz
(2)
@ 14.759 MHz
(2)
@ 10 MHz
(2)
PR
(3)
%Error
PR
(3)
%Error
PR
(3)
%Error
PR
(3)
%Error
9600
153,600
64
-0.16%
32
1.36%
23
0%
15
-1.73%
19200
307,200
32
1.36%
15
-1.73%
11
0%
7
-1.73%
38400
614,400
15
-1.73%
7
-1.73%
5
0%
3
-1.73%
57600
921,600
10
1.36%
4
-8.51%
3
0%
2
9.58%
115200
1,843,200
4
-8.51%
2
-35.6%
1
0%
1
32.18%
Note 1:
Shaded values indicate a % error that is larger than should be used.
2:
The following shows the PICDEM™ Demo Board device frequencies:
PICDEM™ HPC Explorer Demo Board has a 10 MHz crystal installed (4xPLL -> 40 MHz).
PICDEM™ FS USB Demo Board has a 20 MHz crystal installed.
PICDEM™ 2 Plus Demo Board has a 4 MHz crystal installed.
PICDEM™ LCD has a socket for an external canned oscillator (also has an internal 8 MHz RC).
3:
CCP Duty Cycle should be approximately 50% of the PR value.
Desired
Baud Rate
@ 40 MHz
(2)
@ 20 MHz
(2)
@ 14.759 MHz
(2)
@ 10 MHz
(2)
SPBRG
(3)
%Error
SPBRG
(3)
%Error
SPBRG
(3)
%Error
SPBRG
(3)
%Error
9600
225
-1.73%
129
-0.16%
95
0%
64
-0.16%
19200
129
-0.16%
64
-0.16%
47
0%
32
1.36%
38400
64
-0.16%
32
1.36%
23
0%
15
-1.73%
57600
42
-0.94%
21
1.36%
15
0%
10
1.36%
115200
21
1.36%
10
1.36%
7
0%
4
-8.51%
Note 1:
Shaded values indicate a % error that is larger than should be used.
2:
The following shows the PICDEM™ Demo Board device frequencies:
PICDEM™ HPC Explorer Demo Board has a 10 MHz crystal installed (4xPLL -> 40 MHz).
PICDEM™ FS USB Demo Board has a 20 MHz crystal installed.
PICDEM™ 2 Plus Demo Board has a 4 MHz crystal installed.
PICDEM™ LCD has a socket for an external canned oscillator (also has an internal 8 MHz RC).
3:
SYNC = 0, BRGH = 1, BRG16 = 0.
