Rev. 1.10
28
November 26, 2019
Rev. 1.10
29
November 26, 2019
HT68FB240
USB Low Speed Flash MCU
On-Chip Debug Support – OCDS
An EV chip exists for the purposes of device emulation. This EV chip device also provides an
"On-Chip Debug" function to debug the device during the development process. The EV chip
and the actual MCU device are almost functionally compatible except for the "On-Chip Debug"
function. Users can use the EV chip device to emulate the real chip device behavior by connecting
the OCDSDA and OCDSCK pins to the Holtek HT-IDE development tools. The OCDSDA pin is
the OCDS Data/Address input/output pin while the OCDSCK pin is the OCDS clock input pin.
When users use the EV chip for debugging, other functions which are shared with the OCDSDA
and OCDSCK pins in the actual MCU device will have no effect in the EV chip. However, the two
OCDS pins which are pin-shared with the ICP programming pins are still used as the Flash Memory
programming pins for ICP. For a more detailed OCDS description, refer to the corresponding
document named "Holtek e-Link for 8-bit MCU OCDS User’s Guide".
Holtek e-Link Pins
EV Chip Pins
Pin Description
OCDSDA
OCDSDA
On-chip Debug Support Data/Address input/output
OCDSCK
OCDSCK
On-chip Debug Support Clock input
VDD
VDD
Power Supply
GND
VSS
Ground
RAM Data Memory
The Data Memory is a volatile area of 8-bit wide RAM internal memory and is the location where
temporary information is stored.
Structure
Divided into two sections, the first of these is an area of RAM, known as the Special Function Data
Memory. Here are located registers which are necessary for correct operation of the device. Many
of these registers can be read from and written to directly under program control, however, some
remain protected from user manipulation. The second area of Data Memory is known as the General
Purpose Data Memory, which is reserved for general purpose use. All locations within this area are
read and write accessible under program control.
The overall Data Memory is subdivided into two banks. The Special Purpose Data Memory registers
are accessible in all banks, with the exception of the FRCR, FCR, FARH and FDnH
registers
at
address
from 40H to 46H
, which is only accessible in Bank 1. Switching between the different Data
Memory banks is achieved by setting the Bank Pointer to the correct value. The start address of the
Data Memory for the device is the address 00H.
Special Purpose
Data Memory
General Purpose
Data Memory
00H
5FH
60H
FFH
Bank 0
Bank 0
40H~46H
in Bank 1
Data Memory Structure
