p87c591vfb NXP Semiconductors, p87c591vfb Datasheet - Page 61

• Manufacturer Part Number: p87c591vfb
• Description: Single-chip 8-bit Microcontroller With Can Controller
• Manufacturer: NXP Semiconductors

Philips Semiconductors
14.3
There are several possibilities to generate the baud rate
clock for the serial port depending on the mode in which it
is operating.
For clarification some terms regarding the difference
between “baud rate clock” and “baud rate” should be
mentioned. The serial interface requires a clock rate which
is 16 times the baud rate for internal synchronization.
Therefore, the baud rate generators have to provide a
“baud rate clock” to the serial interface which - there
14.3.1
Table 38 Internal Baud Rate Generator Prescaler Low Register S0PSL (address FAH)
Prescaler load value
Table 39 Description of S0PSL bits
Table 40 Internal Baud Rate Generator Prescaler High Register S0PSH (address FBH)
Prescaler higher nibble load value
Table 41 Description of S0PSH bits
14.3.2
Table 42 PCON (address 87H)
Prescaler load value
Table 43 Description of SMOD1 and SMOD0 bits
2000 Jul 26
Single-chip 8-bit microcontroller with CAN controller
7 to 0
6 to 4
3 to 0
SMOD1
5 to 0
BIT
BIT
BIT
SPS
7
7
6
7
7
7
Baud Rate Generation
I
PCON
NTERNAL
SYMBOL
SYMBOL
(POF) to (IDL) Description refer to Section 11.3.5 “Power Control Register (PCON)”.
FOR THE
SYMBOL
SPS
SMOD1
SMOD0
SMOD0
B
AUD
6
6
6
R
I
NTERNAL
ATE
Baud reload low value. Lower 8 bits of the baud rate timer reload value.
Baud rate generator enable. When set, the baud rate of serial interface is derived from
the dedicated baud rate generator. When cleared (default after reset), baud rate is derived
from the Timer 1 overflow rate.
Reserved.
Baud rate generator reload high value. Upper four bits of the baud rate timer value.
G
Double Baud rate. When set, the baud rate of serial interface is modes 1, 2, 3 is
doubled. After reset this bit is cleared.
Double Baud rate. Selects SM0/FE for SCON.7 bit.
ENERATOR
(POF)
B
AUD
5
5
5
R
ATE
P
RESCALER
G
ENERATOR
(WLE)
prescaler load value
4
4
4
S0PSH, S0PSL
61
divided by 16 - results in the actual “baud rate”. However,
all formulas given in the following section already include
the factor and calculate the final baud rate. Further, the
abbreviation f
(oscillator or external input clock operation).
The baud rate of the serial port is controlled by the two bits
SPS and SMOD1 which are located in the Special
Function Registers S0PSH and PCON. In SFRs S0PSH
and S0PSL the prescaler load value of the internal baud
rate generator can be programmed (see Table 38 to 43).
(GF1)
DESCRIPTION
DESCRIPTION
3
3
3
DESCRIPTION
CLK
higher nibble load value
refers to the external clock frequency
(GF0)
2
2
2
Preliminary Specification
(PD)
1
1
1
P8xC591
(IDL)
0
0
0