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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
71 of 1441
NXP Semiconductors
UM10503
Chapter 6: LPC43xx/LPC43Sxx flash programming/ISP and IAP
6.4.5.3 ISP data format
The data stream is in UU-encoded format. The UU-encode algorithm converts 3 B of
binary data in to 4 B of printable ASCII character set. It is more efficient than Hex format
which converts 1 byte of binary data in to 2 bytes of ASCII hex. The sender should send
the check-sum after transmitting 20 UU-encoded lines. The length of any UU-encoded line
should not exceed 61 characters (bytes) i.e. it can hold 45 data bytes. The receiver should
compare it with the check-sum of the received bytes. If the check-sum matches then the
receiver should respond with "OK<CR><LF>" to continue further transmission. If the
check-sum does not match the receiver should respond with "RESEND<CR><LF>". In
response the sender should retransmit the bytes.
6.4.5.4 ISP flow control
A software XON/XOFF flow control scheme is used to prevent data loss due to buffer
overrun. When the data arrives rapidly, the ASCII control character DC3 (0x13) is sent to
stop the flow of data. Data flow is resumed by sending the ASCII control character DC1
(0x11). The host should also support the same flow control scheme.
6.4.5.5 ISP command abort
Commands can be aborted by sending the ASCII control character "ESC" (0x1B). This
feature is not documented as a command under "ISP Commands" section. Once the
escape code is received the ISP command handler waits for a new command.
6.4.5.6 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.
The user should either disable interrupts, or ensure that user interrupt vectors are active in
RAM and that the interrupt handlers reside in RAM, before making a flash erase/write IAP
call. The IAP code does not use or disable interrupts.
6.4.5.7 RAM used by ISP
The boot code uses the local SRAM block at address 0x10080000 as its working area. In
parts with on-chip flash the content of the whole 40 kB SRAM block may be lost upon
reset. In parts without on-chip flash the lower 32 kB of this SRAM block may be lost upon
reset.
6.4.5.8 RAM used by IAP command handler
Flash programming commands use 16 B of RAM from 0x10089FF0 to 0x10089FFF.
Applications making use of IAP calls must reserve this RAM block. The maximum stack
usage in the user allocated stack space is 256 B. The stack space is excluding usage of
IAP Set active partition command. The Set active partition command requires an
additional 2200 B in stack additionally for a maximum of 2456 B.
6.4.6 Flash signature generation
For parts with on-chip flash, a hardware flash signature generation capability is built into
the flash memory. This feature can be used to create a signature that can then be used to
verify flash contents. Details of flash signature generation are shown in