Maxim Integrated MAX31782 - Manual (Page 154)

MaximIntegrated 18-3
MAX31782 User’s Guide
Revision 0; 8/11
SECTION 18: IN-SYSTEM PROGRAMMING
The MAX31782 contains an internal bootstrap loader utilizing the JTAG or I 2 C interfaces . As a result, system software
can be upgraded in-system, eliminating the need for a costly hardware retrofit when software updates are required .
After each device reset, MAX31782 ROM code is executed which determines if bootloader operation is desired .
Figure 18-1 provides information on how the MAX31782 enters into bootloader operation .
Figure 18-1. Entering Bootloader Operation
18.1DetailedDescription
Following every reset, device ROM code is executed that determines if the MAX31782 should enter into a bootloader
mode . First, the ICDF register, which is not cleared by a reset, is read to see if the system programming enable (SPE)
bit is set . See
18.1.2 Entering JTAG Bootloader for more details on setting the SPE bit . If SPE is set, the MAX31782
enters into bootloader operation .
ANY DEVICE RESET OCCURS
BOOTLOADER
SET PSS[1:0] = 01
IS JTAG_SPE
BIT SET?
NO
NO
YES
RESET DEVICE.
BEGIN BOOT ROM CODE
EXECUTION AT 8000h
EXIT BOOTLOADER.
DELAY 128 CLOCK CYCLES.
SET PWL AND ROD BITS.
ROM CODE ENABLE THE
SLAVE I 2 C INTERFACE
JUMP TO USER CODE
(FLASH) AT 0000h
ROM CODE CHECKS FOR A
VALID PASSWORD. PWL BIT
IS SET IF A VALID PASSWORD
IS DETECTED.
YES
EXIT LOADER
COMMAND
IS PSS[1:0]
! = 1X?
SET I2C_SPE BIT
DEVICE HAS NEVER BEEN PROGRAMMED.
WILL AUTOMATICALLY GO TO I 2 C
BOOTLOADER.
IS I2C_SPE
BIT SET?
NO
YES
IS PWL BIT SET?
YES
NO