Rev. 1.71
64
April 11, 2017
Rev. 1.71
65
April 11, 2017
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
System Clock output pin CLO
The device HT66F004 provides a system clock output pin CLO. MCU system clock can output to
the CLO pin by setting pin-shared control register bit PBS4 to 1. The highest output frequency is
8MHz in this device. Please note that when the noise problem is an important issue, it is better not to
use CLO output function.
Programming Considerations
Within the user program, one of the first things to consider is port initialisation. After a reset, all
of the I/O data and port control registers will be set high. This means that all I/O pins will default
to an input state, the level of which depends on the other connected circuitry and whether pull-
high selections have been chosen. If the port control registers are then programmed to setup some
pins as outputs, these output pins will have an initial high output value unless the associated port
data registers are first programmed. Selecting which pins are inputs and which are outputs can be
achieved byte-wide by loading the correct values into the appropriate port control register or by
programming individual bits in the port control register using the “SET [m].i” and “CLR [m].i”
instructions. Note that when using these bit control instructions, a read-modify-write operation takes
place. The microcontroller must first read in the data on the entire port, modify it to the required new
bit values and then rewrite this data back to the output ports.
Port A has the additional capability of providing wake-up functions. When the device is in the
SLEEP or IDLE Mode, various methods are available to wake the device up. One of these is a high
to low transition of any of the Port A pins. Single or multiple pins on Port A can be setup to have this
function.
