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,
R
EQUEST & ACCEPT, control the flow of data in each direction:-
TX Request & TX Accept:
RX Request & RX Accept:
control the flow from the HOST to the SP2 (download)
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:
2. Memory Access:
To the transmitter or from the receiver
To or from the SP2's memory
Byte Count (1-60)
0
0
0
Packet To Transmit
SP2
SP2
Received Packet
3rd data byte
2nd data byte
1st data byte
control byte
Byte Count (1-60)
0
0
7
6
0
6 bits
figure 5: SP2 ↔ Host data transfer
Radiometrix Ltd, SP2 data sheet
page 6
RADIOMETRIX [ RADIOMETRIX LTD ]
