HT68F04 Holtek Semiconductor, HT68F04 Datasheet - Page 17

• Manufacturer Part Number: HT68F04
• Description: Small Package Enhanced Flash Type 8-Bit MCU
• Manufacturer: Holtek Semiconductor

In Circuit Programming
The provision of Flash type Program Memory provides
the user with a means of convenient and easy upgrades
and modifications to their programs on the same device.
As an additional convenience, Holtek has provided a
means of programming the microcontroller in-circuit us-
ing a 5-pin interface. This provides manufacturers with
the possibility of manufacturing their circuit boards com-
plete with a programmed or un-programmed
microcontroller, and then programming or upgrading the
program at a later stage. This enables product manufac-
turers to easily keep their manufactured products sup-
plied with the latest program releases without removal
and re-insertion of the device.
·
tempreg1 db
tempreg2 db
:
:
mov a,06h
mov tblp,a
mov a,07h
:
:
tabrd tempreg1
dec tblp
tabrd tempreg2
:
:
org 700h
dc 00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh
:
:
Rev. 1.00
tbhp,a
MCU Programming Pins
Table Read Program Example
RES
VDD
PA0
PA2
VSS
?
?
; temporary register #1
; temporary register #2
; initialise low table pointer - note that this address
; is referenced
; initialise high table pointer
; transfers value in table referenced by table pointer data at program
; memory address ²706H² transferred to tempreg1 and TBLH
; reduce value of table pointer by one
; transfers value in table referenced by table pointer data at program
; memory address ²705H² transferred to tempreg2 and TBLH in this
; example the data ²1AH² is transferred to tempreg1 and data ²0FH² to
; register tempreg2
; sets initial address of program memory
Serial Data Input/Output
Serial Clock
Device Reset
Power Supply
Ground
Function
HT66F03/HT66F04/HT68F03/HT68F04
17
The Program Memory and EEPROM data memory can
both be programmed serially in-circuit using this 5-wire
interface. Data is downloaded and uploaded serially on
a single pin with an additional line for the clock. Two ad-
ditional lines are required for the power supply and one
line for the reset. The technical details regarding the
in-circuit programming of the devices are beyond the
scope of this document and will be supplied in supple-
mentary literature.
During the programming process the RES pin will be
held low by the programmer disabling the normal opera-
tion of the microcontroller and taking control of the PA0
and PA2 I/O pins for data and clock programming pur-
poses. The user must there take care to ensure that no
other outputs are connected to these two pins.
April 16, 2010
www.DataSheet4U.com