4XR01T3V130 Datasheet, PDF (11/16 Pages) Holtek Semiconductor Inc – 8-Bit OTP MCU with RF Transmitter

HT46R01T3/HT48R01T3
8-Bit OTP MCU with RF Transmitter
Absolute Maximum Ratings
The Absolute Maximum Ratings must be checked for discrepancies and the necessary care taken in
device handling and usage.
Power Supply
Examination of the block diagram will reveal that the Power Supply and Ground pins of the RF
Transmitter and MCU are independent and must be connected together if they are to share the same
power supply. If the same power supply is to be used for both chips then care must be taken as both
have different power supply requirements.
When calculating the total current consumption of the device, the internal DC specification currents
for the MCU and RF parts must be added together.
The RF data to be transmitted is derived from the PB1 line. When the PB1 line is high the device will
transmit allowing users to program their encoded data on this line. If the RF transmitter is in its
standby mode then there will be a delay of about 500ms before transmission begins. When the device
is transmitting, a synchronising signal will be generated on the CREF/PB0 pin which allows the
MCU to use it to calibrate its internal RC oscillator. To avoid the RF circuits entering an unknown
state, pin PB1 should be setup as an output as soon as possible after power-on.
To minimise power consumption, only when PB1 is high, can the RF signal be transmitted and the
reference clock on PB0 be generated. If no data transitions are generated on PB1 for 300~500ms, the
transmitter will enter a standby state and the RF circuits will be switched off along with the internal
PLL to save power. The signal generated on the CREF/PB0 line will also remain at a low level. The
internal PLL function is used to generate the RF frequency with a multiplier of 32 times the crystal
frequency. The relationship is: RF frequency = 32 ´ Crystal frequency. Therefore a 9.84375MHz
crystal will generate an RF frequency of 315MHz and a13.56MHz crystal will generate an RF
frequency of 433.92MHz. All PLL circuits are contained within the device and the only external
component required is a suitable crystal.
Power Down and Wake up
It is important to note that if the MCU is powered down or placed into a low power mode to conserve
power, that the RF Transmitter may continue running and will consume a certain amount of power.
Before powering down the MCU it is important to carefully manage the PB1 pin to ensure the
RF-Transmitter enters its power down state.
Programming Considerations
As MCU lines PB0 and PB1 are used to control the RF transmitter function, care must be taken to
manage these lines correctly in the application program. As line PB1 is used to send data to the RF
circuitry this line must be setup as an output. To avoid erroneous operation of the RF circuits this line
should be setup as an output immediately after power-on. The PB0 pin on the MCU is used to receive
synchronising pulses from the RF circuits and should therefore be setup as an input.
As the MCU will be powered down independently of the RF Transmitter Peripheral Module, care must
be taken to ensure that the MCU first clears its PB1 line to zero before powering down. This will allow
the RF Transmitter Peripheral Module to enter its standby state and thus keep power consumption to a
minimum.
Rev. 1.30
11
November 23, 2010