Holtek HT66F03T3, HT68F03T3 Quick Start Manual
HT66F03T3/68F03T3 MCU with 315MHz/433MHz ASK Transmitter
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HT66F03T3/68F03T3 MCU with
315MHz/433MHz ASK Transmitter
D/N：AN0220E
General Description
The HT66F03T3/68F03T3 is a Flash type MCU with an RF ASK transmitter function. Data
generated from the MCU will be transmitted at a carrier frequency of 315M/433MHz to a
receiver.
Functions
Complete UHF transmitter
Frequency range of 300MHz to 450MHz
Output power up to 10dBm
Low external part count with minimal external components
Low voltage operation (down to 2.2V)
Diagram
Hardware Diagram Description
Output matching circuit: the following example uses a low pass matching circuit.
KEY PAD: the following example uses PA0~PA3 and PA6~PA7 as switch input pins.
HT66F03T3/68F03T3 MCU with 315MHz/433MHz ASK Transmitter
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Application Circuit
The circuit in the frame is the harmonic inhibiting enhancement circuit which can be
ignored if not necessary.
Note: The value in the parentheses is for 433MHz. For example, 433.92MHz the Crystal
Y1 should be 13.56MHz.
Adjust Output Power with External Resistors
R1 in the application circuit is used to adjust the RF output power. In this example, the R1
resistor values for the 50 demo board and corresponding typical values of conducted
RF output levels are listed in the table below. R1 in the HT46/48R01T3 demo board uses
a dipole antenna which can be adjusted to an appropriate radiation to meet the
specifications of the design.
Typical I
D
of PA (mA) Output Power
(dBm)
R1()
433MHz 315MHz
10 0 7.8 8.8
3 390 5.0 5.0
0 560 4.0 4.0
HT66F03T3/68F03T3 MCU with 315MHz/433MHz ASK Transmitter
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Reference Clock (CREF ) Example
The Clock CREF is provided for IRC frequency calibration of the MCU. It is useful for
devices that require accurate frequencies, such as RTC applications. The following
example demonstrates an RF transmission from PA4 with data received on PA5 and
calibrated by CREF.
;; PA4 is the toggle output pin
;; PA5 is the cref intput pin
;; tmr0 is used to counte cref
;; tmr1 is used to generate toggle
#INCLUDE HT48R01B.INC
CREF_DEMO .section 'data'
CA1_TMP DB 1
CA2_TMP DB 1
GEN1_TMR_TMP DB 1
GEN2_TMR_TMP DB 1
PA5_TMP DB 1
CREF_COUNT DB 1
CREF_DEMO .section at 0 'code'
ORG 00H
JMP MAIN
ORG 08H
JMP TMR0INT
org 0ch
JMP TMR1INT
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
;~~~~~~~~~~timer0 int
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
TMR0INT:
SDZ CA1_TMP
JMP POLLIN_PA5
INC CA2_TMP
POLLIN_PA5:
SZ PA5_TMP
JMP HI
LO:
SNZ PA5 ;POLLING PA5 STATUS
JMP NO_CHANGE
SET PA5_TMP
JMP INC_CREF_COUNT
HI:
SZ PA5 ;POLLING PA5 STATUS
JMP NO_CHANGE
CLR PA5_TMP
JMP INC_CREF_COUNT
INC_CREF_COUNT:
SDZ CREF_COUNT
JMP EXIT
CLR ACC
SUBM A,CA1_TMP
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