Si4430/31/32-B1
Rev 1.1
43
6.3.  Packet Handler TX Mode
If the TX packet length is set the packet handler will send the number of bytes in the packet length field before
returning  to  IDLE  mode  and  asserting  the  packet  sent  interrupt.  To  resume sending  data  from  the  FIFO  the
microcontroller needs to command the chip to re-enter TX mode. Figure 19 provides an example transaction where
the packet length is set to three bytes.
Figure 19. Multiple Packets in TX Packet Handler
6.4.  Packet Handler RX Mode
6.4.1. Packet Handler Disabled
When  the  packet  handler  is  disabled  certain  fields  in  the  received  packet  are  still  required.  Proper  modem
operation requires preamble and sync when the FIFO is being used, as shown in Figure 20. Bits after sync will be
treated as raw data with no qualification. This mode allows for the creation of a custom packet handler when the
automatic qualification parameters are not sufficient. Manchester encoding is supported but data whitening, CRC,
and header checks are not.
Figure 20. Required RX Packet Structure with Packet Handler Disabled
6.4.2. Packet Handler Enabled 
When the packet handler is enabled, all the fields of the packet structure need to be configured. Register contents
are  used  to  construct  the  header  field  and  length  information  encoded  into  the  transmitted  packet  when
transmitting. The receive FIFO can be configured to handle packets of fixed or variable length with or without a
header. If multiple packets are desired to be stored in the FIFO, then there are options available for the different
fields that will be stored into the FIFO. Figure 21 demonstrates the options and settings available when multiple
packets are enabled. Figure 22 demonstrates the operation of fixed packet length and correct/incorrect packets. 
Figure 21. Multiple Packets in RX Packet Handler
ata 1
ata 2
ata 3
ata 4
ata 5
ata 6
ata 7
ata 8
ata 9
}
}
}
This will be sent in the first transmission
This will be sent in the second transmission
This will be sent in the third transmission
Preamble
SYNC
DATA
Register
Data
Register
Data
FIFO
Data
Header(s)
Length
rx_multi_pk_en = 1
H
Data
rx_multi_pk_en = 0
txhdlen = 0
txhdlen > 0
fixpklen
fixpklen
0    1
0
1
Data
Data
Data
Data
L
L
H
RX FIFO Contents:
Transmission: