AT89LP4052 Atmel Corporation, AT89LP4052 Datasheet - Page 29

• Manufacturer Part Number: AT89LP4052
• Manufacturer: Atmel Corporation

Specifications of AT89LP4052

• Flash (kbytes): 4 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 15
• Spi: 1
• Uart: 1
• Sram (kbytes): 0.25
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 2
• Isp: SPI
• Watchdog: Yes

Table 16-3.
16.5
3547J–MICRO–10/09
Bit
Symbol
PWM1EN
PWM0EN
PSC12
PSC11
PSC10
PSC02
PSC01
PSC00
TCONB = 91H
Not Bit Addressable
Pulse Width Modulation
PWM1EN
7
Configures Timer 1 for Pulse Width Modulation output on T1 (P3.5).
Configures Timer 0 for Pulse Width Modulation output on T0 (P3.4).
Prescaler for Timer 1 Mode 0. The number of active bits in TL1 equals PSC1 + 1. After reset PSC1 = 100B which
enables 5 bits of TL1 for compatibility with the 13-bit Mode 0 in AT89S2051.
Prescaler for Timer 0 Mode 0. The number of active bits in TL0 equals PSC0 + 1. After reset PSC0 = 100B which
enables 5 bits of TL0 for compatibility with the 13-bit Mode 0 in AT89C52.
Function
TCONB
– Timer/Counter Control Register B
PWM0EN
Timer 0 and Timer 1 may be independently configured as 8-bit asymmetrical pulse width modu-
lators (PWM) by setting the PWM0EN or PWM1EN bits in TCONB, respectively. In PWM Mode
the generated waveform is output on the timer's pin, T0 or T1. C/T must be set to “0” when in
PWM mode. In Timer 0's PWM mode, TH0 acts as an 8-bit counter while RH0 stores the 8-bit
compare value. When TH0 is 00H the PWM output is set high. When the TH0 count reaches the
value stored in RH0 the PWM output is set low. Therefore, the pulse width is proportional to the
value in RH0. To prevent glitches writes to RH0 only take effect on the FFH to 00H overflow of
TH0. Timer 1 has the same behavior using TH1 and RH1. See
example. Setting RH0 to 00H will keep the PWM output low.
The PWM will only function if the timer is in Mode 0 or Mode 1. In Mode 0, TL0 acts as a logarith-
mic prescaler driving TH0 (see
value. In Mode 1, TL0 provides linear prescaling with an 8-bit auto-reload from RL0 (see
16-7).
Figure 16-5. Asymmetrical Pulse Width Modulation
6
PSC12
5
PSC11
4
Figure
PSC10
16-6). The PSC0 bits in TCONB control the prescaler
3
PSC02
2
AT89LP2052/LP4052
Counter Value (TH0)
Reset Value = 0010 0100B
Figure 16-5
PSC01
1
Compare Value (RH0)
PWM Output (T0)
for PWM waveform
PSC00
0
Figure
29