UM11029
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© NXP B.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
46 of 515
NXP Semiconductors
UM11029
Chapter 5: LPC84x ISP and IAP
5.7.3 I2C ISP mode transaction protocol
The LPC84x will respond to a host system on I2C addresses 0x18, 0x1C, 0x30, and 0x38.
The host system’s I2C master clock rate can be as high as 1MHz. The LPC84x may
extend the I2C clock to delay the I2C master if it needs more time to perform an operation.
When using I2C, the command is given to the LPC84x by an I2C write transaction. The
entire command packet is accepted by the LPC84x and then processing starts. Once the
LPC84x has completed processing, it may drive the ISP1_IRQ line low until the host
system issues an I2C read transaction to get the response.
5.7.4 SPI ISP mode transaction protocol
The LPC84x will respond to a host system on the configured SPI interface. A transfer is
started once SSEL goes low on the LPC84x. The SPI clock to the LPC84x should not
exceed 2MHz. SPI SSEL to first clock timing should not be less than 100uS. SPI transfer
configuration should be SPI Mode 0 with 8 data bits.
SPI transactions are bi-directional. During the command packet phase, the host system
should ignore the read data (send data from LPC84x). During the response phase, the
LPC84x will ignore the read data (send data from host).
Although SPI is bi-directional, the command and response packet phases only send data
one way for each phase. During the command packet phase, a single SPI transfer occurs
where the command and data is sent from the host system. In this phase, SSEL is
asserted low, the command packet is sent, and then SSEL is deasserted. The host
system then waits for ISP1_IRQ to go low from the LPC84x. Once ISP1_IRQ goes low,
the host system then asserts SSEL low, the response packet is read, and then SSEL is
deasserted. The LPC84x will deassert ISP1_IRQ at the start of the response packet prior
to the response packet completing transfer.
Fig 6.
Typical host system and LPC84x transaction
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