AT89S8253 Atmel Corporation, AT89S8253 Datasheet - Page 19
![no-image](/images/manufacturer_photos/0/0/79/atmel_corporation_sml.jpg)
AT89S8253
Manufacturer Part Number
AT89S8253
Description
Manufacturer
Atmel Corporation
Datasheets
1.AT89S8253.pdf
(60 pages)
2.AT89S8253.pdf
(2 pages)
3.AT89S8253.pdf
(2 pages)
4.AT89S8253.pdf
(2 pages)
Specifications of AT89S8253
Flash (kbytes)
12 Kbytes
Max. Operating Frequency
24 MHz
Cpu
8051-12C
Max I/o Pins
32
Spi
1
Uart
1
Sram (kbytes)
0.25
Eeprom (bytes)
2048
Operating Voltage (vcc)
2.7 to 5.5
Timers
3
Isp
SPI
Watchdog
Yes
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
AT89S8253-24AC
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
Part Number:
AT89S8253-24AI
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
Company:
Part Number:
AT89S8253-24AU
Manufacturer:
ATMEL
Quantity:
6 250
Part Number:
AT89S8253-24AU
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
Company:
Part Number:
AT89S8253-24JC
Manufacturer:
ATMEL
Quantity:
5 530
Company:
Part Number:
AT89S8253-24JC
Manufacturer:
ATM
Quantity:
3 290
Company:
Part Number:
AT89S8253-24JC
Manufacturer:
ATMEL
Quantity:
6 988
Part Number:
AT89S8253-24JC
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
12. Programmable Clock Out
Figure 12-1. Timer 2 in Clock-out Mode
3286P–MICRO–3/10
Timer 2 as a baud rate generator is shown in
TCLK = 1 in T2CON. Note that a rollover in TH2 does not set TF2 and will not generate an inter-
rupt. Note too, that if EXEN2 is set, a 1-to-0 transition in T2EX will set EXF2 but will not cause a
reload from (RCAP2H, RCAP2L) to (TH2, TL2). Thus when Timer 2 is in use as a baud rate gen-
erator, T2EX can be used as an extra external interrupt.
Note that when Timer 2 is running (TR2 = 1) as a timer in the baud rate generator mode, TH2 or
TL2 should not be read from or written to. Under these conditions, the Timer is incremented
every state time, and the results of a read or write 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.
A 50% duty cycle clock can be programmed to come out on P1.0, as shown in
pin, besides being a regular I/O pin, has two alternate functions. It can be programmed to input
the external clock for Timer/Counter 2 or to output a 50% duty cycle clock ranging from 61 Hz to
4 MHz (for a 16 MHz operating frequency).
To configure the Timer/Counter 2 as a clock generator, bit C/T2 (T2CON.1) must be cleared and
bit T2OE (T2MOD.1) must be set. Bit TR2 (T2CON.2) starts and stops the timer.
The clock-out frequency depends on the oscillator frequency and the reload value of Timer 2
capture registers (RCAP2H, RCAP2L), as shown in the following equation.
In the clock-out mode, Timer 2 rollovers will not generate an interrupt. This behavior is similar to
when Timer 2 is used as a baud-rate generator. It is possible to use Timer 2 as a baud-rate gen-
erator and a clock generator simultaneously. Note, however, that the baud-rate and clock-out
frequencies cannot be determined independently from one another since they both use
RCAP2H and RCAP2L.
Clock Out Frequency
=
------------------------------------------------------------------------------------------- -
4
×
[
Figure
65536
Oscillator Frequency
–
10-4. This figure is valid only if RCLK or
(
RCAP2H,RCAP2L
)
]
AT89S8253
Figure
12-1. This
19