SM5958 Datasheet, PDF (49/53 Pages) SyncMOS Technologies,Inc – Enhance user code protection

SM5958
8-Bit Micro-controller
32KB with ISP Flash
& 1KB RAM embedded
14. In-System Programming (Internal ISP)
The SM5958 can generate flash control signal by internal hardware circuit. Users utilize flash control register, flash
address register and flash data register to perform the ISP function without removing the SM5958 from the system.
The SM5958 provides internal flash control signals which can do flash program/chip erase/page erase/protect
functions. User need to design and use any kind of interface which SM5958 can input data. User then utilize ISP
service program to perform the flash program/chip erase/page erase/protect functions.
14.1 ISP service program
The ISP service program is a user developed firmware program which resides in the ISP service program space.
After user developed the ISP service program, user then determine the size of the ISP service program. User need
to program the ISP service program in the SM5958 for the ISP purpose.
The ISP service programs were developed by user so that it should includes any features which relates to the flash
memory programming function as well as communication protocol between SM5958 and host device which output
data to the SM5958. For example, if user utilize UART interface to receive/transmit data between SM5958 and host
device, the ISP service program should include baud rate, checksum or parity check or any error-checking
mechanism to avoid data transmission error.
14.2 Lock Bit (N)
The Lock Bit N has two functions: one is for service program size configuration and the other is to lock the ISP
service program space from flash erase function.
The ISP service program space address range $7000 to $7FFF. It can be divided as blocks of N*512 byte. (N=0 to
8). When N=0 means no ISP function, all of 4K byte flash memory can be used as program memory. When N=1
means ISP service program occupies 512 byte while the rest of 3.5K byte flash memory can be used as program
memory. The maximum ISP service program allowed is 4K byte when N=8. Under such configuration, the usable
program memory space is 4K byte.
The lock bit N function is different from the flash protect function. The flash erase function can erase all of the flash
memory except for the locked ISP service program space. If the flash not has been protected, the content of ISP
service program still can be read. If the flash has been protected, the overall content of flash program memory
space including ISP service program space can not be read. As given in Table 14-1.
Table 14-1 ISP code area
ISP service program address
0 No ISP service program
1 512 bytes ($7E00h ~ $7FFFh)
2 1K bytes ($7C00h ~ $7FFFh)
3 1.5K bytes ($7A00h ~ $7FFFh)
4 2K bytes ($7800h ~ $7FFFh)
5 2.5K bytes ($7600h ~ $7FFFh)
6 3K bytes ($7400h ~ $7FFFh)
7 3.5K bytes ($7200h ~ $7FFFh)
8 4 K bytes ($7000h ~ $7FFFh)
ISP service program configurable in N*512 byte (N= 0 ~ 8)
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M089
Ver C SM5958 04/17/2015
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