hcs512 Microchip Technology Inc., hcs512 Datasheet - Page 10

• Manufacturer Part Number: hcs512
• Description: Keeloq Code Hopping Decoder Keeloq Code Hopping Decoder
• Manufacturer: Microchip Technology Inc.

HCS512
6.2
The manufacturer’s code must be programmed into
EEPROM memory through the synchronous program-
ming interface using the DATA and CLK lines. Provision
must be made for connections to these pins if the
decoder is going to be programmed in circuit.
Programming mode is activated if the CLK is low for at
least 1 ms and then goes high within 64 ms after power-
up, stays high for longer than 8 ms but not longer than
128 ms. After entering Programming mode the 64-bit
manufacturer’s code, 8-bit configuration byte, and 8-bit
checksum is sent to the device using the synchronous
interface. After receiving the 80-bit message the check-
sum is verified and the information is written to
EEPROM. If the programming operation was success-
ful, the HCS512 will respond with an Acknowledge
pulse.
After programming the manufacturer’s code, the
HCS512 decoder will automatically activate an
Erase All function, removing all transmitters from the
system.
6.3
The manufacturer’s code and configuration byte must
be downloaded Least Significant Byte, Least Signifi-
cant bit first as shown in Table 6-3.
FIGURE 6-1:
DS40151D-page 10
Check-
Byte 9
sum
Programming the Manufacturer’s
Code
Download Format
Byte 8
Config
CHECKSUM CALCULATION
Byte 7
Key_7
Man
01
24
69
D0
59
04
D1
C0
(FF
Byte 6
Key_6
16
Man
16
16
16
16
16
16
16
16
+ 23
+ 45
+ 67
+ AB
+ CD
+ EF
+ 89
+ 1
- C1
16
16
16
16
16
16
16
16
16
= C1
= 24
= 69
= D0
) + 1
= 159
= 104
= D1
= 1C0
Byte 5
Key_5
Man
16
6
16
16
16
16
16
16
(Carry is discarded)
16
= 3F
(Carry is discarded)
(Carry is discarded)
16
Byte 4
Key_4
Man
6.4
The checksum is used by the HCS512 to check that the
data downloaded was correctly received before pro-
gramming the data. The checksum is calculated so that
the 10 bytes added together (discarding the overflow
bits) is zero. The checksum can be calculated by add-
ing the first 9 bytes of data together and subtracting the
result from zero. Throughout the calculation the over-
flow is discarded.
Given
89ABCDEF
checksum is calculated as shown in Figure 6-1. The
checksum is 3F
6.5
The HCS512 decoder will automatically add a test
transmitter each time an Erase All Function is done. A
test transmitter is defined as a transmitter with a serial
number of zero. After an Erase All, the test transmitter
will always work without learning and will not check the
synchronization counter of the transmitter. Learning of
any new transmitters will erase the test transmitter.
TABLE 6-3:
Note 1: A transmitter with a serial number of zero
a
Checksum
Test Transmitter
2: Always learn at least one transmitter after
Byte 3
Key_3
Byte 0, right-most bit downloaded first.
Man
16
cannot be learned. Learn will fail after the
first transmission.
an Erase All sequence. This ensures that
the test transmitter is erased.
manufacturer’s
and a Configuration Word of 1
16
.
DOWNLOAD DATA
Byte 2
Key_2
Man
2002 Microchip Technology Inc.
code
Byte 1
Key_1
Man
of
01234567-
Byte 0
Key_0
Man
16
, the