hcs515 Microchip Technology Inc., hcs515 Datasheet - Page 11

• Manufacturer Part Number: hcs515
• Description: Keeloq Code Hopping Decoder Keeloq Code Hopping Decoder
• Manufacturer: Microchip Technology Inc.

4.2.5
The read command (Figure 4-4) is used to read bytes
from the user EEPROM. The offset in the user
EEPROM is specified by the address byte, which is
truncated to 7 bits (C to D). After the address, a dummy
byte must be clocked in (D to E). The EEPROM data
byte is clocked out on the next rising edge of the clock
line with the Least Significant bit first (E to F). Sequen-
tial reads are possible by repeating sequence E to F
within 1 ms after the falling edge of the previous byte’s
Most Significant bit (MSb). During the sequential read,
the address value will wrap after 128 bytes. The
decoder will terminate the read command if no clock
pulses are received for a period longer than 1.2 ms.
FIGURE 4-4:
FIGURE 4-5:
Decoder DATA
2002 Microchip Technology Inc.
Decoder DATA
C DATA
C DATA
CLK
READ BYTE/S FROM USER
EEPROM
CLK
A
START Command
A
START Command
READ BYTES FROM USER EEPROM
WRITE BYTES TO USER EEPROM
B
B
LSB
LSB
Command Byte
Command Byte
MSB
MSB
C
C
LSB
LSB
Address Byte
Address Byte
MSB
4.2.6
The write command (Figure 4-5) is used to write a loca-
tion in the user EEPROM. The address byte is trun-
cated to seven bits (C to D). The data is clocked in
Least Significant bit (LSb) first. The clock line must be
asserted to initiate the write. Sequential writes of bytes
are possible by clocking in the byte and then asserting
the clock line (D – F). The decoder will terminate the
write command if no clock pulses are received for a
period longer than 1.2 ms After a successful write
sequence, the decoder will acknowledge by taking the
data line high and keeping it high until the clock line
goes low.
MSB
D
D
LSB
LSB
WRITE BYTE/S TO USER EEPROM
Data Byte
Dummy Byte
MSB
MSB
T
T
WR
RD
E
E
LSB
HCS515
Acknowledge
T
Data Byte
ACK
DS40183D-page 11
T
T
RESP
ACK
2
MSB
T
RD
F
F