P87LPC764BD NXP Semiconductors, P87LPC764BD Datasheet - Page 34

• Manufacturer Part Number: P87LPC764BD
• Description: MCU 8-Bit 87LP 80C51 CISC 4KB EPROM 5V 20-Pin SO Tube
• Manufacturer: NXP Semiconductors

Specifications of P87LPC764BD

• Package: 20SO
• Device Core: 80C51
• Family Name: 87LP
• Maximum Speed: 20 MHz
• Ram Size: 128 Byte
• Program Memory Size: 4 KB
• Operating Supply Voltage: 5 V
• Data Bus Width: 8 Bit
• Program Memory Type: EPROM
• Number Of Programmable I/os: 18
• Interface Type: I2C/UART
• Operating Temperature: 0 to 70 °C
• Number Of Timers: 2

Philips Semiconductors
Baud Rates
The baud rate in Mode 0 is fixed: Mode 0 Baud Rate = CPU clock/6.
The baud rate in Mode 2 depends on the value of bit SMOD1 in
Special Function Register PCON. If SMOD1 = 0 (which is the value
on reset), the baud rate is 1/32 of the CPU clock frequency. If
SMOD1 = 1, the baud rate is 1/16 of the CPU clock frequency.
Using Timer 1 to Generate Baud Rates
When Timer 1 is used as the baud rate generator, the baud rates in
Modes 1 and 3 are determined by the Timer 1 overflow rate and the
value of SMOD1. The Timer 1 interrupt should be disabled in this
Table 9. Baud Rates, Timer Values, and CPU Clock Frequencies for SMOD1 = 0
2003 Sep 03
Low power, low price, low pin count (20 pin)
microcontroller with 4 kbyte OTP
Timer Co nt
Timer Count
Mode 2 Baud Rate + 1 ) SMOD1
–10
–1
–2
–3
–4
–5
–6
–7
–8
–9
* 1.8432
* 3.6864
0.4608
0.9216
1.3824
2.3040
2.7648
3.2256
4.1472
4.6080
2400
32
CPU clock frequency
* 3.6864
* 7.3728
0.9216
1.8432
2.7648
4.6080
5.5296
6.4512
8.2944
9.2160
4800
* 14.7456
* 18.4320
* 11.0592
* 1.8432
* 3.6864
* 7.3728
12.9024
16.5888
5.5296
9.2160
9600
33
application. The Timer itself can be configured for either “timer” or
“counter” operation, and in any of its 3 running modes. In the most
typical applications, it is configured for “timer” operation, in the
auto-reload mode (high nibble of TMOD = 0010b). In that case the
baud rate is given by the formula:
Tables 6 and 7 list various commonly used baud rates and how they
can be obtained using Timer 1 as the baud rate generator.
Baud Rate
Mode 1, 3 Baud Rate +
* 11.0592
* 14.7456
* 18.4320
* 3.6864
* 7.3728
19.2k
–
–
–
–
–
* 14.7456
* 7.3728
38.4k
192 (or 96 if SMOD1 + 1)
–
–
–
–
–
–
–
–
CPU clock frequency
256 * (TH1)
P87LPC764
* 11.0592
57.6k
Product data
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–
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–
–
–
–
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