p89v51rb2 NXP Semiconductors, p89v51rb2 Datasheet - Page 37

• Manufacturer Part Number: p89v51rb2
• Description: 8-bit 80c51 5 V Low Power 16/32/64 Kb Flash Microcontroller With 1 Kb Ram
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89V51RB2_RC2_RD2_4
Product data sheet
6.5.5 Summary of baud rate equations
6.6.1 Mode 0
6.6 UARTs
not cause a reload from (RCAP2H, RCAP2L) to (TH2,TL2). Therefore when Timer 2 is in
use as a baud rate generator, T2EX can be used as an additional external interrupt, if
needed.
When Timer 2 is in the baud rate generator mode, one should not try to read or write TH2
and TL2. Under these conditions, a read or write of TH2 or TL2 may not be accurate. The
RCAP2 registers may be read, but should not be written to, because a write might overlap
a reload and cause write and/or reload errors. The timer should be turned off (clear TR2)
before accessing the Timer 2 or RCAP2 registers.
rates and how they can be obtained from Timer 2.
Timer 2 is in baud rate generating mode. If Timer 2 is being clocked through pin T2 (P1.0)
the baud rate is:
If Timer 2 is being clocked internally, the baud rate is:
Where f
To obtain the reload value for RCAP2H and RCAP2L, the above equation can be rewritten
as:
Table 24.
The UART operates in all standard modes. Enhancements over the standard 80C51
UART include Framing Error detection, and automatic address recognition.
Serial data enters and exits through RXD and TXD outputs the shift clock. Only 8 bits are
transmitted or received, LSB first. The baud rate is fixed at
UART configured to operate in this mode outputs serial clock on TXD line no matter
whether it sends or receives data on RXD line.
Rate
750 kBd
19.2 kBd
9.6 kBd
4.8 kBd
2.4 kBd
600 Bd
220 Bd
600 Bd
220 Bd
Baud rate = Timer 2 overflow rate / 16
Baud rate = f
RCAP2H, RCAP2L = 65536
osc
Timer 2 generated commonly used baud rates
= oscillator frequency
osc
/ (16
Osc freq
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
6 MHz
6 MHz
Rev. 04 — 1 May 2007
(65536
f
osc
(RCAP2H, RCAP2L)))
/ (16
P89V51RB2/RC2/RD2
baud rate)
Timer 2
RCAP2H
FF
FF
FF
FF
FE
FB
F2
FD
F9
8-bit microcontrollers with 80C51 core
Table 24
1
shows commonly used baud
6
of the CPU clock frequency.
RCAP2L
FF
D9
B2
64
C8
1E
AF
8F
57
© NXP B.V. 2007. All rights reserved.
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