HCS101
Fixed Code Encoder
FEATURES
Operating
•
•
•
•
•
•
•
•
•
2 Programmable 32-bit serial numbers
10-bit serial number
66-bit transmission code length
Non-volatile 16-bit counter
3.5V -13.3V operation
3 inputs, 7 functions available
Selectable baud rate
Automatic code word completion
Battery low signal transmitted to receiver
The 8-pin HCS101 operates over a wide voltage range
of 3.5V to 13.3V and has three button inputs allowing
the system designer the freedom to utilize up to 7 func-
tions. The only components required for device opera-
tion are the buttons and RF circuitry, allowing a very low
system cost.
PACKAGE TYPES
PDIP, SOIC
S0
S1
S2
NC
1
HCS101
2
3
4
8
7
6
5
V
DD
NC
DATA
V
SS
Other
•
•
•
•
•
•
Pin-out compatible with most K
EE
L
OQ®
Encoders
Simple programming interface
On-chip EEPROM
On-chip oscillator and timing components
Button inputs have internal pull-down resistors
Minimum External Components required
HCS101 BLOCK DIAGRAM
Oscillator
Controller
RESET Circuit
Power
latching
and
switching
Typical Applications
The HCS101 is ideal for remote control applications.
These applications include:
•
•
•
•
•
•
•
Low-end automotive alarm systems
Low-end automotive immobilizers
Gate and garage door openers
Identity tokens
Low-end burglar alarm systems
Fan and lighting controls
Toys
EEPROM
DATA
Transmit register
V
SS
V
DD
Button input port
S2
S1
S0
DESCRIPTION
The HCS101 from Microchip Technology Inc. is a fixed
code encoder designed for remote control systems. It
provides a small package outline and low cost to make
this device a perfect solution for unidirectional remote
control systems.
It is also pin compatible with Microchip’s HCS201 Code
Hopping Encoder allowing easy upgrading to a more
secure remote keyless entry (RKE) system.
2001 Microchip Technology Inc.
Preliminary
DS41115C-page 1
©
HCS101
1.0
SYSTEM OVERVIEW
The EEPROM data for each transmitter is programmed
by the manufacturer at the time of production.
Any type of controller may be used as a receiver, but it
is typically a microcontroller with compatible firmware
that allows the receiver to operate in conjunction with a
transmitter, based on the HCS101.
As indicated in the block diagram in Figure 1-1, the
HCS101 has a small EEPROM array, which must be
loaded with several parameters before use. These
parameters include:
•
•
•
•
Two 32-bit serial numbers
16-bit counter value
Additional 10-bit serial number
Configuration data
FIGURE 1-1:
BASIC OPERATION OF TRANSMITTER ENCODER
Transmitted Information
Serial
Function
Number 3
Bits
Function
Bits
Counter
Serial Number 1
EEPROM Array
Serial Number 3
Counter
Serial Number 1
©
DS41115C-page 2
Preliminary
2001 Microchip Technology Inc.
HCS101
2.0
DEVICE OPERATION
As shown in the typical application circuits in Figure 2-
1, the HCS101 is easy to use. It requires only the addi-
tion of buttons and RF circuitry for use as the transmit-
ter in your application. A description of each pin is given
in Table 2-1.
The HCS101 will wake-up upon detecting a switch clo-
sure and then delay for a debounce delay (T
DB
) as
shown in Figure 2-2. The device will then update the
16-bit counter before it loads the transmit register. The
data is then transmitted serially on the DATA pin in
Pulse Width Modulation (PWM) format.
If additional buttons are pressed during a transmission,
the current transmission is terminated. The HCS101
restarts and the new transmission will contain the latest
button information. When all buttons are released, the
device completes the current code word and then pow-
ers down. Released buttons do not terminate and/or
restart transmissions.
FIGURE 2-1:
V
DD
TYPICAL CIRCUITS
B0
B1
S0
S1
S2
NC
V
DD
NC
DATA
V
SS
Tx out
FIGURE 2-2:
ENCODER OPERATION
(A button has been pressed)
Power-Up
RESET and Debounce Delay
Sample Inputs
V
DD
2 button remote control
B3 B2 B1 B0
Update Counter
Load Transmit Register
S0
S1
S2
NC
V
DD
NC
DATA
V
SS
Tx out
Transmit
Yes
Buttons
Added
?
No
All
No
Buttons
Released
?
Yes
Complete Code
Word Transmission
Stop
4 button remote control
Note:
Up to 7 functions can be implemented
by pressing more than one button
simultaneously or by using a suitable
diode array.
TABLE 2-1:
Pin
Name
Number
S0
S1
S2
NC
V
SS
DATA
1
2
3
4
5
6
PIN DESCRIPTIONS
Description
Switch input 0
Switch input 1
Switch input 2/Clock pin for
Programming mode
No connection
Ground reference connection
Pulse Width Modulation (PWM)
output pin/Data pin for
Programming mode
No connection
Positive supply voltage connection
NC
V
DD
7
8
2001 Microchip Technology Inc.
Preliminary
DS41115C-page 3
©
HCS101
3.0
3.1
TRANSMITTED WORD
Transmission Format (PWM Mode)
3.2
Code Word Organization
The HCS101 transmission is made up of several code
words as shown in Figure 3-1. Each code word starts
with a preamble and a header, followed by the data.
The code word is followed by a guard period before the
next code word begins. The same code word is trans-
mitted as long as the button is pressed. Refer to
Table 7-3 for transmission timing requirements.
The HCS101 transmits a 66-bit code word. The 66-bit
word is constructed from the serial numbers, counter
and function information. The code word format is
shown in Figure 3-2.
Under normal conditions, serial number 1 is transmitted
with the counter and serial number 3. If all the buttons
are pressed, serial number 2 is transmitted in place of
the counter and serial number 3.
FIGURE 3-1:
T
E
CODE WORD TRANSMISSION FORMAT
LOGIC ‘0’
LOGIC ‘1’
Bit
Period
Preamble
Tp
Header
Th
Counter, SER_3
and Function
SER_1
and Function
Guard
Time
Tg
Start Pulse
(Te)
FIGURE 3-2:
CODE WORD ORGANIZATION
‘1’
(1 bit)
V
LOW
(1 bit)
Function**
(0/4 bits)
Serial Number 1
(32/28 bits)**
Counter
(16 bits)
Function
(4 bits)
S2 S1 S0 S3*
‘00’
(2 bits)
Serial Number 3
(10 bits)
S2 S1 S0 S3*
Serial Number 2***
(32 bits)
LSb
Transmission Direction
LSb first
MSb
* See Section 4.3.6, S3 Setting (S3SET)
** See Section 4.3.7 Extended Serial Number (XSER)
*** Serial Number 2 is transmitted when all buttons are pressed
©
DS41115C-page 4
Preliminary
2001 Microchip Technology Inc.
HCS101
4.0
EEPROM MEMORY
ORGANIZATION
TABLE 4-2:
Bit Number
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
CONFIGURATION WORD
Bit Name
OSC0
OSC1
OSC2
OSC3
V
LOWS
BRS
MTX4
TXEN
S3SET
XSER
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
The HCS101 contains 192 bits (12 x 16-bit words) of
EEPROM memory as shown in Table 4-1. Further
descriptions of the memory array are given in the fol-
lowing sections.
TABLE 4-1:
WORD
ADDRESS
0
1
2
3
4
5
6
7
8
9
10
11
EEPROM MEMORY MAP
MNEMONIC
RESERVED
RESERVED
RESERVED
RESERVED
CNTR
RESERVED
SER_1
SER_1
SER_2
SER_2
SER_3
CONFIG
DESCRIPTION
Set to 0000H
Set to 0000H
Set to 0000H
Set to 0000H
Counter
Set to 0000H
Device Serial Number 1
(word 0) 16 LSb’s
Device Serial Number 1
(word 1) 16 MSb’s
Device Serial Number 2
(word 0) 16 LSb’s
Device Serial Number 2
(word 1) 16 MSb’s
Device Serial Number 3
Config Word
4.3.1
OSCILLATOR TUNING BITS
(OSC0 TO OSC3)
These bits are used to tune the nominal frequency of
the HCS101 to within ±10% of its nominal value over
temperature and voltage.
4.3.2
LOW VOLTAGE TRIP POINT
SELECT (V
LOWS
)
The low voltage trip point select bit (V
LOWS
) and the S3
setting bit (S3SET) are used to determine the voltage
level for the low voltage detector.
V
LOWS
0
0
1
1
* See also Section 4.3.6
S3SET*
0
1
0
1
Trip Point
4.4
4.4
9
6.75
4.1
CNTR (Counter)
This is the 16-bit gray code counter value that can be
used to track the number of times a transmitter has
been activated.
4.2
SER_1, SER_2, SER_3 (Encoder
Serial Number)
SER_1, and SER_2 are the 32-bit device serial num-
bers. SER_3 is an additional 10-bit serial number trans-
mitted with every transmission. The most significant 6
bits of the 16-bit SER_3 word are reserved and should
be set to zero.
4.3.3
BAUDRATE SELECT BITS (BRS)
4.3
Configuration Word
BRS selects the speed of transmission and the code
word blanking. Table 4-3 shows how the bit is used to
select the different baud rates and Section 5.2 provides
a detailed explanation of code word blanking.
The configuration word is a 16-bit word stored in the
EEPROM array that is used by the device to store the
status configuration options. Further explanations of
each of the bits are described in the following sections.
TABLE 4-3:
BRS
0
1
BAUDRATE SELECT
Basic Pulse
Element
400µs
200µs
Code Words
Transmitted
All
1 out of 2
2001 Microchip Technology Inc.
Preliminary
DS41115C-page 5
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