ViewSonic VE720m-1 Service Manual page 33

7. Boot code of ISP
7.1 Hardware ISP
(1) Without boot code
(2) Fixed security code: 94, 94, AC, CA, 53
(3) Attention to the pin of HSCL (1) and HSDA (1) should keep in enable
(4) MTV412M, MTV512M, CS8954 support hardware ISP
7.2 Software ISP
(1) With boot code
(2) User define the security code
(3) Attention to the pin of HSCL (1) and HSDA (1) should keep in enable
(4) Only software ISP could read the MCU content
(5) MTV212M, MTV312M, MTV230M, MTV412M, MTV512M, CS8954 support software ISP
7.3 Boot code of software ISP
(1) Initialize MCU
(a) Define the I/O pin to HSCL (1) and HSDA (1)
(b) Define the slave B address
(c) Enable 8051 INT1 (ISR 2)
(2) Coding for INT1 while get into ISP mode
(a) Clear watchdog to prevent reset during ISP period
(b) Disable all interrupt to prevent CPU wake-up
(c) Write ISP slave address
(d) Write 93h to ISP enable address to enable ISP
(e) Enter 8051 idle mode
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