UM11029
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© NXP B.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
25 of 515
NXP Semiconductors
UM11029
Chapter 5: LPC84x ISP and IAP
If FAIM content is invalid, the default ISP selection is USART/I2C/SPI or auto detection
mode. In auto detection mode, the LPC84x enables all three interfaces on the fixed GPIO
port and pins, and selects the first one that has either a successful auto baud detection on
USART or a valid probe message response on I2C or SPI.
If FAIM content is valid, USART, I2C, or SPI ISP mode is configured in the FAIM.
Additional SWM configuration for the interface and pins through FAIM is required. For
example, if FAIM ISP selection is 0x02, the GPIO port and pin information for SPI0, such
as SSEL, SCK, MOSI, and MISO is provided by the FAIM. The boot ROM reads the GPIO
port and pin information from the FAIM and writes to the SWM and IOCON registers
accordingly as part of the SPI initialization.
5.3.7 ISP interrupt and SRAM use
5.3.7.1 Interrupts during IAP
The on-chip flash memory is not accessible during erase/write operations. When the user
application code starts executing, the interrupt vectors from the user flash area are active.
Before making any IAP call, either disable the interrupts or ensure that the user interrupt
vectors are active in RAM and that the interrupt handlers reside in RAM. The IAP code
does not use or disable interrupts.
5.3.7.2 RAM used by ISP command handlers
The stack of UART ISP commands is located at address 0x1000 0600. The maximum
stack usage is 1280 bytes (0x500) and grows downwards.
The DMA is used by the SPI ISP mode. The DMA descriptor table location is located at
address 0x1000 0600. The DMA table size is 512 bytes (0x200) and grows upwards.
Therefore, depending on the ISP mode entered, the maximum RAM used by ISP mode is
2 K starting from the address 0x1000 0000.
Memory for the USART and I2C/SPI ISP commands is allocated dynamically.