P89C668 Philips Semiconductors, P89C668 Datasheet - Page 15

• Manufacturer Part Number: P89C668
• Description: 80C51 8-bit Flash microcontroller family 64KB ISP FLASH with 8KB RAM
• Manufacturer: Philips Semiconductors

1. Capture/reload occurs only on timer/counter overflow.
2. Capture/reload occurs on timer/counter overflow and a 1-to-0 transition on T2EX (P1.1) pin except when Timer 2 is used in the baud rate
Philips Semiconductors
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.
Table 5 shows commonly used baud rates and how they can be
obtained from Timer 2.
Summary Of Baud Rate Equations
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:
Table 6.
Table 7.
NOTES:
2001 Jul 27
80C51 8-bit Flash microcontroller family
64KB ISP Flash with 8KB RAM
16-bit Auto-Reload
16-bit Capture
Baud rate generator receive and transmit same baud rate
Receive only
Transmit only
16-bit
Auto-Reload
generator mode.
Baud Rate + Timer 2 Overflow Rate
Baud Rate +
Timer 2 as a Timer
Timer 2 as a Counter
[16
[65536 * (RCAP2H, RCAP2L)]]
16
MODE
MODE
f
OSC
15
Except for the baud rate generator mode, the values given for T2CON
Where f
To obtain the reload value for RCAP2H and RCAP2L, the above
equation can be rewritten as:
Timer/Counter 2 Set-up
do not include the setting of the TR2 bit. Therefore, bit TR2 must be
set, separately, to turn the timer on. see Table 6 for set-up of Timer 2
as a timer. Also see Table 7 for set-up of Timer 2 as a counter.
INTERNAL CONTROL
INTERNAL CONTROL
RCAP2H, RCAP2L + 65536 *
(Note 1)
(Note 1)
OSC
00H
01H
34H
24H
14H
02H
03H
= Oscillator Frequency
T2CON
TMOD
EXTERNAL CONTROL
EXTERNAL CONTROL
32
Baud Rate
f
OSC
(Note 2)
(Note 2)
0AH
0BH
08H
09H
36H
26H
16H
P89C668
Preliminary data