P89LV51RD2BA PHILIPS [NXP Semiconductors], P89LV51RD2BA Datasheet - Page 37

• Manufacturer Part Number: P89LV51RD2BA
• Description: 8-bit 80C51 3 V low power 64 kB Flash microcontroller with 1 kB RAM
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 14342
Product data
7.4.5 Summary of baud rate equations
7.5 UARTs
The Timer 2 as a baud rate generator mode is valid only if RCLK and/or TCLK =
T2CON register. Note that a rollover in TH2 does not set TF2, and will not generate
an interrupt. Thus, the Timer 2 interrupt does not have to be disabled when Timer 2 is
in the 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.
shows commonly used baud 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.
Baud rate
750K
19.2K
9.6K
4.8K
2.4K
600
220
600
220
Baud rate = Timer 2 overflow rate / 16
Baud rate = f
RCAP2H, RCAP2L = 65536
osc
Timer 2 generated commonly used baud rates
= oscillator frequency
osc
Rev. 04 — 02 December 2004
/ (16
Osc freq
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
6 MHz
6 MHz
(65536
f
osc
(RCAP2H, RCAP2L)))
/ (16
P89LV51RB2/RC2/RD2
Timer 2
RCAP2H
FF
FF
FF
FF
FE
FB
F2
FD
F9
baud rate)
8-bit microcontrollers with 80C51 core
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
RCAP2L
FF
D9
B2
64
C8
1E
AF
8F
57
Table 24
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