p89c538nbb NXP Semiconductors, p89c538nbb Datasheet - Page 11

• Manufacturer Part Number: p89c538nbb
• Description: Cmos Single-chip 8-bit Microcontrollers With Flash Program Memory
• Manufacturer: NXP 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
When Timer 2 is in the baud rate generator mode, one should not try
to read or write TH2 and TL2. As a baud rate generator, Timer 2 is
incremented every state time (osc/2) or asynchronously from pin T2;
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.
Table 4 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:
Table 5. Timer 2 as a Timer
Table 6. Timer 2 as a Counter
NOTES:
1998 Apr 24
80C51 8-bit microcontroller family
16K/64K/512 FLASH
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
16
MODE
MODE
11
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:
Timer/Counter 2 Set-up
Except for the baud rate generator mode, the values given for
T2CON do not include the setting of the TR2 bit. Therefore, bit TR2
must be set, separately, to turn the timer on. see Table 5 for set-up
of Timer 2 as a timer. Also see Table 6 for set-up of Timer 2 as a
counter.
INTERNAL CONTROL
INTERNAL CONTROL
Baud Rate +
RCAP2H, RCAP2L + 65536 *
(Note 1)
(Note 1)
OSC
00H
01H
34H
24H
14H
02H
03H
= Oscillator Frequency
[32
[65536 * (RCAP2H, RCAP2L)]]
T2CON
TMOD
f
OSC
89C536/89C538
EXTERNAL CONTROL
EXTERNAL CONTROL
32
Baud Rate
f
OSC
Preliminary specification
(Note 2)
(Note 2)
0AH
0BH
08H
09H
36H
26H
16H