C8051F121 Silicon Laboratories Inc, C8051F121 Datasheet - Page 320

• Manufacturer Part Number: C8051F121
• Description: IC 8051 MCU FLASH 128K 64TQFP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F12xr

Specifications of C8051F121

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 100MHz
• Connectivity: EBI/EMI, SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 32
• Program Memory Size: 128KB (128K x 8)
• Program Memory Type: FLASH
• Ram Size: 8.25K x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 3.6 V
• Data Converters: A/D 8x8b, 8x12b; D/A 2x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TQFP, 64-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

C8051F120/1/2/3/4/5/6/7
C8051F130/1/2/3
23.2.4. Toggle Output Mode (Timer 2 and Timer 4 Only)
Timers 2 and 4 have the capability to toggle the state of their respective output port pins (T2 or T4) to pro-
duce a 50% duty cycle waveform output. The port pin state will change upon the overflow or underflow of
the respective timer (depending on whether the timer is counting up or down ). The toggle frequency is
determined by the clock source of the timer and the values loaded into RCAPnH and RCAPnL. When
counting DOWN, the auto-reload value for the timer is 0xFFFF, and underflow will occur when the value in
the timer matches the value stored in RCAPnH:RCAPnL. When counting UP, the auto-reload value for the
timer is RCAPnH:RCAPnL, and overflow will occur when the value in the timer transitions from 0xFFFF to
the reload value.
To output a square wave, the timer is placed in reload mode (the Capture/Reload Select Bit in TMRnCN
and the Timer/Counter Select Bit in TMRnCN are cleared to ‘0’). The timer output is enabled by setting the
Timer Output Enable Bit in TMRnCF to ‘1’. The timer should be configured via the timer clock source and
reload/underflow values such that the timer overflow/underflows at 1/2 the desired output frequency. The
port pin assigned by the crossbar as the timer’s output pin should be configured as a digital output (see
Section “18. Port Input/Output” on page 235
of the pin. A Read/Write of the Timer’s Toggle Output State Bit (TMRnCF.2) is used to read the state of the
toggle output, or to force a value of the output. This is useful when it is desired to start the toggle of a pin in
a known state, or to force the pin into a desired state when the toggle mode is halted.
320
Equation 23.1. Square Wave Frequency (Timer 2 and Timer 4 Only)
F
sq
=
------------------------------------------------------
2

). Setting the timer’s Run Bit (TRn) to ‘1’ will start the toggle

Rev. 1.4
65536 RCAPn
F
TCLK
–
