SP2-433-160 Datasheet, PDF (6/27 Pages) Radiometrix Ltd – UHF SpacePort Transceiver

2.2 HOST TO SP2 DATA TRANSFER
Data is transferred between the SP2 and the HOST 4 bits (nibbles) at a time using a fully asynchronous
protocol. The nibbles are always sent in pairs to form a byte, the Least Significant Nibble (bits 0 to 3) is
transferred first, followed by the Most Significant Nibble (bits 4 to 7). Two pairs of handshake lines,
REQUEST & ACCEPT, control the flow of data in each direction:-
TX Request & TX Accept: control the flow from the HOST to the SP2 (download)
RX Request & RX Accept: control the flow from the SP2 to the HOST (upload)
A packet transferred between host and SP2 consists of between 1 and 61 bytes, the first byte of the
packet is always the control byte.
There are two classes of HOST ↔ SP2 transfers:
1. Data Packets: To the transmitter or from the receiver
2. Memory Access: To or from the SP2's memory
0 0 0 Byte Count (1-60)
Packet To Transmit
SP2
figure 5: SP2 ↔ Host data transfer
SP2
Received Packet
3^rd data byte
2^nd data byte
1^st data byte
control byte 0 0
Byte Count (1-60)
76
0
6 bits
Radiometrix Ltd, SP2 data sheet
page 6