ST72521 STMICROELECTRONICS [STMicroelectronics], ST72521 Datasheet - Page 137

• Manufacturer Part Number: ST72521
• Description: 8-BIT MCU WITH NESTED INTERRUPTS, FLASH, 10-BIT ADC, FIVE TIMERS, SPI, SCI, I2C, CAN INTERFACE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

CONTROLLER AREA NETWORK (Cont’d)
BAUD RATE PRESCALER REGISTER (BRPR)
Read/Write in Standby mode
Reset Value: 00h
RJW[1:0] determine the maximum number of time
quanta by which a bit period may be shortened or
lengthened to achieve resynchronization.
t
BRP[5:0] determine the CAN system clock cycle
time or time quanta which is used to build up the in-
dividual bit timing.
t
Where t
The resulting baud rate can be computed by the for-
mula:
Note: Writing to this register is allowed only in
Standby mode to prevent any accidental CAN pro-
tocol violation through programming errors.
RJW
CAN
RJW1 RJW0
7
BR
= t
= t
CPU
CAN
=
CPU
----------------------------------------------------------------------------------------------- -
t
CPU
* (BRP + 1)
* (RJW + 1)
= time period of the CPU clock.
BRP5
BR P
BRP4
+
1
BRP3
1
BS1
BRP2
+
BS2
BRP1
+
3
BRP0
0
BIT TIMING REGISTER (BTR)
Read/Write in Standby mode
Reset Value: 23h
BS2[2:0] determine the length of Bit Segment 2.
t
BS1[3:0] determine the length of Bit Segment 1.
t
Note: Writing to this register is allowed only in
Standby mode to prevent any accidental CAN pro-
tocol violation through programming errors.
PAGE SELECTION REGISTER (PSR)
Read/Write
Reset Value: 00h
PAGE[2:0] determine which buffer or filter page is
mapped at addresses 0010h to 001Fh.
BS2
BS1
7
0
7
0
PAGE2
= t
= t
0
0
0
0
1
1
1
1
CAN
CAN
BS22
0
* (BS2 + 1)
* (BS1 + 1)
BS21
0
PAGE1
0
0
1
1
0
0
1
1
BS20
0
BS13
0
PAGE0
0
1
0
1
0
1
0
1
PAGE
BS12
2
PAGE
BS11
ST72521
Page Title
Diagnosis
Reserved
Reserved
Reserved
1
Buffer 1
Buffer 2
Buffer 3
Filters
137/211
PAGE
BS10
0
0
0