SM5953
8-Bit Micro-controller
15KB with ISP Flash
& 256B RAM embedded
12.3 Program the ISP Service Program
After Lock Bit N is set and ISP service program been programmed, the ISP service program memory will be
protected (locked) automatically. The lock bit N has its own program/erase timing. It is different from the flash
memory program/erase timing so the locked ISP service program can not be erased by flash erase function. If user
needs to erase the locked ISP service program, he can do it by writer only. User can not change ISP service
program when SM5953 was in system.
12.4 Initiate ISP Service Program
To initiate the ISP service program is to load the program counter (PC) with start address of ISP service program
and execute it. There are four ways to do so:
(1) Blank reset. Hardware reset with first flash address blank ($0000=#FFH) will load the PC with start
address of ISP service program.
(2) Execute jump instruction can load the start address of the ISP service program to PC.
(3) RESET is asserted with P2.6 and P2.7 both at low state. User can change enable or disable by writer.
During the strobe window, the hardware will detect the status of P2.6 and P2.7. If they meet one of above
conditions, chip will switch to ISP mode automatically. After ISP service program executed, user need to reset the
SM5953, either by hardware reset or by WDT, or jump to the address $0000 to re-start the firmware program.
12.5 ISP register – ISPFAH, ISPFAL, ISPFD and ISPC
Mnemonic
ISPFAH
Description
ISP Flash
Address – High
register
ISP Flash
Address - Low
register
ISP Flash Data
register
Dir.
F4h
F5h
Bit 7
Bit 6
ISP function
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
RST
00H
00H
ISPFAH [7:0]
ISPFAL
ISPFAL [7:0]
ISPFD [7:0]
ISPFD
ISPC
F6h
F7h
00H
00H
ISP Control
register
START
-
-
-
-
-
ISPF[1:0]
Address: F4H
Mnemonic: ISPFAH
7
6
5
4
3
2
1
0
Reset
00H
ISPFAH7
ISPFAH6
ISPFAH5
ISPFAH4
ISPFAH3
ISPFAH2
ISPFAH1
ISPFAH0
ISPFAH [7:0]: Flash address-high for ISP function
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M074 Ver B SM5953 12/27/2013
- 39 -
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
