MCRF450/451/452/455
6.2 Anti-collision Command
Controller
This section discusses the anti-collision algorithm and
describes the communications between the
Interrogator and device.
6.2.1
STRUCTURE OF READ/ WRITE
COMMAND SIGNALS
The Interrogator’s Read/Write commands have the
following structure:
Read/Write command = Command + Address + Data + Parity (or CRC)
The commands are summarized in the table below:
TABLE 6-2: READ/WRITE COMMANDS FROM INTERROGATOR TO DEVICE
Interrogator
Command
Command
Code
Address
Data
Parity or CRC
Unused
Read 32-bit block
0xx
xxxxx
—
—
110
aaaaa
—
Parity
Unused
111
00xxx
—
—
Unused
End Process
Unused
Unused
Unused
111
0100x
—
—
111
01010
—
Parity
111
01011
—
—
111
011xx
—
—
111
1000x
—
—
Set Talk First Bit
111
10010
—
Parity
Set FR Bit
111
10011
—
Parity
Clear Talk First Bit
111
10100
—
Parity
Clear FR Bit
111
10101
—
Parity
Unused
111
1011x
—
—
Unused
111
11xxx
—
—
Unused
100
Write 32-bit block
101
Legend: aaaaa = Block address
x = don’t care
xxxxx
aaaaa
—
32 bits
—
CRC-16
Note:
• Command and address are sent MSN (Most
Significant nibble) first.
• Data and parity/CRC are sent LSN (Least
Significant nibble) first.
• Calculation of Parity and CRC includes Command
code, Address, and Data.
• See Microchip Application Note AN752
(DS00752) for the CRC-16 calculation algorithm.
Symbol
Length
—
3 symbols
—
—
3 symbols
—
—
—
3 symbols
3 symbols
3 symbols
3 symbols
—
—
—
14 symbols
DS40232H-page 20
2003 Microchip Technology Inc.