HCS412I MICROCHIP [Microchip Technology], HCS412I Datasheet - Page 24

• Manufacturer Part Number: HCS412I
• Description: KEELOQ Code Hopping Encoder and Transponder
• Manufacturer: MICROCHIP [Microchip Technology]

HCS412
4.3.4
A Bulk Erase resets the HCS412’s memory map to all
zeros. The transponder reader selects the appropriate
device through anticollision, as need be, issues the
PROGRAM command followed by the device’s 28-bit
transport code, then resets the device by removing the
field for 100 ms.
FIGURE 4-7:
4.3.5
Inductive programming a HCS412 begins with a bulk
erase sequence (Section 4.3.4), followed by issuing
the PROGRAM command and the desired EEPROM
memory map’s 18x16-bit words (Section 5.0). The
HCS412 will send a write Acknowledge after each word
has been successfully written, indicating the device is
ready to receive the next 16-bit word.
After a complete 18 word memory map has been
received and written, the HCS412 PPM modulates 18
bursts of 16-bit words on the LC pins for write verifica-
TABLE 4-6:
FIGURE 4-8:
DS41099C-page 24
Command
01000
Communication from reader to HCS412
Communication from HCS412 to reader
Communication from reader to HCS412
Communication from HCS412 to reader
BULK ERASE
PROGRAM
Activate
Activate
Field
Field
Program HCS412 EEPROM
T
T
PU
PU
BULK ERASE
PROGRAM COMMANDS
PROGRAM SEQUENCE - FIRST WORD
ACK
ACK
ACK
ACK
Description
Command
Command
Delay to
Delay to
2 LF
2 LF
T
Start
T
Start
ATO
ATO
TE
TE
Command
Command
Command
Program
Command
Program
Transport code (28 bits); Com-
plete memory map: 18 x 16-bit
Preliminary
2 LF
2 LF
Start
Start
Expected data In
Delay to
TCODE
Delay to
TCODE
words (288 bits)
T
T
OTD
OTD
TE
TE
Resetting the device after the PROGRAM command
results in a bulk erase, resetting the EEPROM memory
map to all zeros. This is important to remember as the
reader must now communicate to the device using the
communication options resulting from a zero’d configu-
ration word - baud rates, modulation format, etc.
(Table 5-1).
tion. Each word follows the standard HCS412 response
format with a leading 1LF
preamble (Figure 4-10).
Since the bulk erase resets the configuration options to
all zeros, the oscillator tuning value will also be cleared.
The correct tuning value is required when the program-
ming sequence sends the new configuration word. The
value may either be obtained by reading the configura-
tion word prior to bulk erase to extract the value or by
determining T
and
(Section 4.2.1).
Transport
Transport
Transport
Transport
Code
Code
28-bit
28-bit
28-bit
28-bit
Code
Code
calculating
Delay to
2 LF
Start
Delay
Data
6ms
T
E
TTD
TE
from the field Acknowledge sequence
Repeat 18 times for programming
the
Write Acknowledge pulse after
each 16-bit word, 288 bits trans-
mitted in 18 bursts of 16-bit words
16 bits Data
Data Bits
16
TE
tuning
2002 Microchip Technology Inc.
low START pulse and ‘01b’
100ms
Device Reset
Response
Delay before Write
Write ACK
value
Write Delay
T
WR
appropriately
ACK
ACK