HCS500-I Datasheet, PDF (11/34 Pages) Microchip Technology – KEELOQ Code Hopping Decoder

HCS500
4.2.5
READ BYTE/S FROM USER
EEPROM
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 seven 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).
Sequential 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) bit. 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.
4.2.6 WRITE BYTE/S TO USER EEPROM
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 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.
FIGURE 4-4: READ BYTES FROM USER EEPROM
TRD
TRD
CLK
µC DATA
LSB
MSB LSB
MSB LSB
MSB
Decoder
DATA
Start Command
A
B
Command Byte
C
LSB
MSB
Address Byte
Dummy Byte
Data Byte
D
E
F
FIGURE 4-5: WRITE BYTES TO USER EEPROM
TWR
CLK
µC DATA
LSB
MSB
LSB
MSB
LSB
MSB
Decoder
DATA
Start Command
Command Byte
Address Byte
Data Byte
A
B
C
D
E
TACK
TRESP
TACK2
Acknowledge
F
© 2002 Microchip Technology Inc.
DS40153C-page 11