p89v660 NXP Semiconductors, p89v660 Datasheet - Page 48

• Manufacturer Part Number: p89v660
• Description: P89v660/p89v662/p89v664 8-bit 80c51 5 V Low Power 16 Kb/32 Kb/64 Kb Flash Microcontroller With 512 B/1 Kb/2 Kb Ram, Dual I2c-bus, Spi
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89V660_662_664_2
Product data sheet
6.6.5 Summary of baud rate equations
6.7 UARTs
baud rate generator mode. Also if the EXEN2 (T2 external enable flag) is set, a 1-to-0
transition in T2EX (Timer/counter 2 trigger input) will set EXF2 (T2 external flag) but will
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 36.
The UART operates in all standard modes. Enhancements over the standard 80C51
UART include Framing Error detection, and automatic address recognition.
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
Rev. 02 — 29 January 2008
Oscillator frequency
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
6 MHz
6 MHz
(65536
f
osc
80C51 with 512 B/1 kB/2 kB RAM, dual I
(RCAP2H, RCAP2L)))
/ (16
baud rate)
Timer 2
RCAP2H
FF
FF
FF
FF
FE
FB
F2
FD
F9
Table 36
P89V660/662/664
shows commonly used baud
RCAP2L
FF
D9
B2
64
C8
1E
AF
8F
57
© NXP B.V. 2008. All rights reserved.
2
C-bus, SPI
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