zic2410 California Eastern Laboratories, zic2410 Datasheet - Page 67

• Manufacturer Part Number: zic2410
• Description: Single-chip Solution, Compliant With Zigbee
• Manufacturer: California Eastern Laboratories

ZIC2410 Datasheet
Figure 32 shows the quadrature signal modulated.
Figure 32 – Quadrature Modulated Signal
The modulated signal is converted to analog by the DAC and then passed to RF block.
The output signal of the DAC is fed to the Quadrature (I/Q) Up-conversion Mixer through the
Low Pass Filter (LPF) and then amplified by the Power Amplifier (PA) and transmitted to the
antenna.
When an RF signal is received by the antenna, it is amplified by the Low Noise Amplifier (LNA)
in the RF block. It is then down-converted to a base-band signal by the Quadrature Down-
conversion Mixer. After low pass filtering, the analog signal is amplified through the Variable
Gain Amplifier (VGA), and converted to a digital signal by the ADC.
The output signal of the ADC is digitally demodulated by the modem block. Digital
demodulation process includes for example, Automatic Gain Control (AGC), De-spreading,
Symbol Detection, and Timing Synchronization. When a frame delimiter is detected on the
demodulated signal, a modem block generates the interrupt which indicates the start of a
packet.
The length and the frame body followed by frame delimiter are stored in RX FIFO of MAC.
When the last data is stored, an interrupt is generated to indicate the end of packet reception.
After a packet reception interrupt occurs, a user can read the data in TX FIFO by software.
When a packet is received, a modem block provides Received Signal Strength Indication (RSSI)
automatically. RSSI is measured by averaging the power level of received signal for a defined
period of time.
It can be used as a Link Quality Indicator (LQI) to decide the quality of the communication
channel.
RSSI is stored in a special register and the stored RSSI value is kept until a new packet is
received. After a packet reception interrupt occurs, a user can read the value stored in RSSI
register by software. While a packet is not being received, the modem block continuously
provides the RSSI of the RF signal at antenna. Measured RSSI is used to decide the
communication channel state. Clear Channel Assessment (CCA) operation is based on this
information. The CCA operation is used to prevent a collision when multiple-users try to use a
channel simultaneously. When a channel is determined to be busy, packet transmission is
deferred until the channel state changes to idle.
Rev A
Document No. 0005-05-07-00-000
Page 67 of 119