HCS500 Datasheet, PDF (10/24 Pages) Microchip Technology – KEELOQ CODE HOPPING ENCODER

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 trun-
cated 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 keep-
ing 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
Address Byte
D
Dummy Byte
LSB
MSB
Data Byte
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
DS40153B-page 10
Preliminary
© 1997 Microchip Technology Inc.