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LPC2917_19_1
© NXP B.V. 2007. All rights reserved.
Preliminary data sheet
Rev. 1.01 — 15 November 2007
27 of 68
NXP Semiconductors
LPC2917/19
ARM9 microcontroller with CAN and LIN
8.4.4.4
UART clock description
The UART modules are clocked by two different clocks; CLK_SYS_PESS and
CLK_UARTx (x = 0-1), see
Section 7.2.2
. Note that each UART has its own CLK_UARTx
branch clock for power management. The frequency of all CLK_UARTx clocks is identical
since they are derived from the same base clock BASE_CLK_UART. The register
interface towards the system bus is clocked by CLK_SYS_PESS. The baud generator is
clocked by the CLK_UARTx.
8.4.5 Serial peripheral interface
8.4.5.1
Overview
The LPC2917/19 contains three Serial Peripheral Interface modules (SPIs) to allow
synchronous serial communication with slave or master peripherals.
The key features are:
•
Master or slave operation
•
Supports up to four slaves in sequential multi-slave operation
•
Supports timer-triggered operation
•
Programmable clock bit rate and prescale based on SPI source clock
(BASE_SPI_CLK), independent of system clock
•
Separate transmit and receive FIFO memory buffers; 16 bits wide, 32 locations deep
•
Programmable choice of interface operation: Motorola SPI or Texas Instruments
Synchronous Serial Interfaces
•
Programmable data-frame size from 4 to 16 bits
•
Independent masking of transmit FIFO, receive FIFO and receive overrun interrupts
•
Serial clock-rate master mode: fserial_clk
≤
f
CLK(SPI)*
/2
•
Serial clock-rate slave mode: fserial_clk = f
CLK(SPI)*
/4
•
Internal loopback test mode
8.4.5.2
Functional description
The SPI module is a master or slave interface for synchronous serial communication with
peripheral devices that have either Motorola SPI or Texas Instruments Synchronous
Serial Interfaces.
The SPI module performs serial-to-parallel conversion on data received from a peripheral
device. The transmit and receive paths are buffered with FIFO memories (16 bits wide x
32 words deep). Serial data is transmitted on SPI_TxD and received on SPI_RxD.
The SPI module includes a programmable bit-rate clock divider and prescaler to generate
the SPI serial clock from the input clock CLK_SPIx.
The SPI module’s operating mode, frame format, and word size are programmed through
the SLVn_SETTINGS registers.
A single combined interrupt request SPI_INTREQ output is asserted if any of the
interrupts are asserted and unmasked.