In Circuit Programming - Holtek HT45F23A Manual

HT45F23A/HT45F24A
TinyPower Flash MCU with OPA & Comparators
TM
Table Read Program Example
tempreg1 db ?
tempreg2 db ?
:
:
mov a,06h
mov tblp,a
mov a, 0Fh
mov tbhp, a
:
:
tabrdl tempreg1
dec tblp
tabrdl tempreg2
:
:
org F00h
dc 00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh
:
:

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 devices. As an additional convenience,
Holtek has provided a means of programming the microcontroller in-circuit using a 5-pin interface.
This provides manufacturers with the possibility of manufacturing their circuit boards complete with
a programmed or un-programmed microcontroller, and then programming or upgrading the program
at a later stage. This enables product manufacturers to easily keep their manufactured products
supplied with the latest program releases without removal and re-insertion of the devices.
The Program Memory can 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
additional 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 supplementary literature.
During the programming process the RES pin will be held low by the programmer disabling the
normal operation of the microcontroller and taking control of the PA0 and PA2 I/O pins for data
and clock programming purposes. The user must there take care to ensure that no other outputs are
connected to these two pins.
Rev. 1.40
; temporary register #1
; temporary register #2
; initialise table pointer - note that this address is referenced
; to the last page or present page
; initialise high table pointer
; transfers value in table referenced by table pointer to tempregl
; data at prog. memory address "0F06H" transferred to tempreg1 and TBLH
; reduce value of table pointer by one
; transfers value in table referenced by table pointer to tempreg2
; data at prog.memory address "0F05H" transferred to tempreg2 and TBLH
; in this example the data "1AH" is transferred to tempreg1 and data "0FH"
; to register tempreg2 the value "00H" will be transferred to the high
; byte register TBLH
; sets initial address of last page
Programming Pins
DATA Serial Data Input/Output
CLK Serial Clock
RES Device Reset
VDD Power Supply
VSS Ground
25
Function
March 29, 2019