HCS512-SLASHP datasheet(10/26 Pages) MICROCHIP

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HCS512

DS40151D-page 10

6.2

Programming the Manufacturer’s

Code

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

Erase All function, removing all transmitters from the

system.

6.3

Download Format

The manufacturer’s code and configuration byte must

be downloaded Least Significant Byte, Least Signifi-

cant bit first as shown in Table 6-3.

6.4

Checksum

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

manufacturer’s

code

01234567-

89ABCDEF16 and a Configuration Word of 116, the

checksum is calculated as shown in Figure 6-1. The

checksum is 3F16.

6.5

Test Transmitter

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:

DOWNLOAD DATA

FIGURE 6-1:

CHECKSUM CALCULATION

Note 1: A transmitter with a serial number of zero

cannot be learned. Learn will fail after the

first transmission.

2: Always learn at least one transmitter after

an Erase All sequence. This ensures that

the test transmitter is erased.

Byte 9

Byte 8

Byte 7

Byte 6

Byte 5

Byte 4

Byte 3

Byte 2

Byte 1

Byte 0

Check-

sum

Config

Man

Key_7

Man

Key_6

Man

Key_5

Man

Key_4

Man

Key_3

Man

Key_2

Man

Key_1

Man

Key_0

Byte 0, right-most bit downloaded first.

0116 + 2316 = 246

2416 + 4516 = 6916

6916 + 6716 = D016

D016 + 8916 = 15916

5916 + AB16 = 10416 (Carry is discarded)

0416 + CD16 = D116 (Carry is discarded)

D116 + EF16 = 1C016

C016 + 116 = C116 (Carry is discarded)

(FF16 - C116) + 116 = 3F16

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