NXP Semiconductors LPC288 Series Manuale utente

AN10548

Getting started with LPC288x

Rev. 01 — 8 January 2007 Application note

Document information

Info Content

Keywords LPC2880, LPC2888, Flash, Interrupt handling, Timer, CGU

Abstract This application note provides code examples for the various peripherals

of the LPC288x. This application note also makes an attempt to draw a

comparison of the LPC288x with the other devices of the LPC2000 family

NXP Semiconductors AN10548

Getting started with LPC288x

Revision history

Rev Date Description

01 20070108 Initial version

Contact information

For additional information, please visit: http://www.nxp.com

For sales office addresses, please send an email to: [email protected]

Application note Rev. 01 — 8 January 2007 2 of 25

NXP Semiconductors AN10548

Getting started with LPC288x

1. Introduction

The LPC288x (LPC2880/LPC2888) includes an ARM7TDMI CPU with an 8 kB cache.

The LPC2888 includes a 1 MB Flash memory system. It has an on-chip DC-to-DC

converter that can generate the required voltages from a single battery or from USB

power. Some other important peripherals are a high-speed USB 2.0 device interface, I2S

interface, SD/MMC card interface and 16-bit stereo A/D and D/A converters (with

amplification and gain control).

In many ways, the LPC2888/LPC2880 is different compared to other devices in the

LPC2000 family. The LPC288x differs in the clocking structure; interrupt handling and

flash programming (to list a few). So code written for an LPC2000 device may not

necessarily work for the LPC288x without modifications.

This application note attempts to cover the various aspects that need to be considered

while writing an application for the LPC288x or porting existing software from any

LPC2000 family device to the LPC288x.

The various topics covered in this application note are as follows:

1. Basic assembly startup code

2. Port pins

3. Clock Generation Unit (CGU)

4. Interrupt handling using Cache and Timer0

5. Flash programming

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Getting started with LPC288x

2. Basic startup code

The startup assembly code for the LPC288x is similar to the other LPC2000 devices

since it is also based on the ARM7TDMI-S architecture. One has to of course take into

consideration that the on-chip Flash and the on-chip SRAM start from address

0x1040 0000 and 0x40 0000, respectively, so the stack pointers and heap should be

arranged accordingly. In other LPC2000 devices, the Flash begins from 0x0 and the

SRAM starts from 0x4000 0000.

There are seventeen locations in the Clock Generation Unit (CGU) module which need to

be initialized to 0 to reduce the overall power consumption. In the header file, these

locations have been addressed as X1 to X17.

In a typical LPC2000 device startup file, one might also find code for initializing the PLL

and the Memory Accelerator module (MAM). This cannot be used for the LPC288x since

the clocking structure is more involved which includes seven input clocks and two

different PLLs. Also there is no MAM in the LPC288x.

Application note Rev. 01 — 8 January 2007 4 of 25

NXP Semiconductors AN10548

Getting started with LPC288x

3. Port pins

The LPC288x has 89 GPIO pins that are split into 8 ports (Port0 to Port7). Some major

differences in the port structure are as follows:

1. In other LPC2000 devices all the port pins were initialized to their GPIO configuration

on reset. In LPC288x, four port pins come up as GPIO and the rest are initialized to

their Functional IO settings. The four pins that are configured to GPIO belong to

Port2.

In LPC2000, to toggle port pins one has to set the direction of the pin (IODIRx) as output

and use IOSETx and IOCLRx respectively to drive the pin high and low.In LPC288x,

there are two-register bits m1 and m2, which need to be set to do the same operation.

The table below shows 2 register bits and their corresponding impact on port pins:

Table 1. M1/M0 settings

m1 m1 Pin state

0 0 GP in (not driven)

0 1 Functional I/O

1 0 GP out (drive LOW)

1 1 GP out (drive HIGH)

As shown above, m1 has to be set and if we toggle the m0 bit, then the corresponding

port pins will toggle.

3.1 Code example

Below is a code snippet showing how the 4 port pins of Port2 can be toggled in software.

1 /* Setting Port2 as “GP out (drive low)” */

2 MODE1S-2=0xF;

3 MODE0C-2=0x0;

5 /* To toggle the pins, just set and reset bit m2 */

6 while(1)

7 {

8 MODE0S-2=0xF;

9 MODE0C-2=0xF;

10 }

4. Clock Generation Unit (using UART)

The CGU is the most important block of the LPC288x and it controls the clocks for the

different modules of this device. The CGU is not present in any of the other LPC2000

devices.

4.1 Basic configuration

For a basic configuration of the CGU the following steps need to be carried out:

1. PLL registers: (optional)

a. Configure either the Main PLL or the high speed PLL if higher speeds are

expected for the application.

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NXP Semiconductors AN10548

Getting started with LPC288x

2. Selection stage registers:

a. Use the respective Frequency Select register to select one of the 7 input clocks.

b. The Switch Configuration and Switch Status registers would be typically used

while dynamic clock switching (shown below with an example).

3. Spreading stage registers: (optional)

a. Power control/Power status/ Enable Select and Software Reset registers would

not be typically used for a basic CGU configuration.

An application is provided below that shows how to configure the CGU for the UART

peripheral. The UART is initially set to work with the 12 MHz oscillator input and then the

clock source is dynamically and gracefully switched between the 32.768 KHz oscillator

input and the output of the main PLL (60 MHz). This application is built for the Nohau

evaluation board, details of which can be found by browsing to the “Support & tools”

section of:

http://www.nxp.com/pip/LPC2880FET180.html#support

The board has a UART port, which should be connected to the PC serial port using a

Null modem cable. The output is captured on Tera Term Pro v2.3 (similar to

HyperTerminal) and it is set to run at the serial baud rate of 600 baud.

4.2 Code example

3 /* Header file for LPC288X */

4 #include"LPC288x.h"

6 /* Used by UART */

7 #define TEMT (1<<6)

8 #define LINE_FEED 0xA

9 #define CARRIAGE_RET 0xD

11 void CGU(void);

12 void switch_clk(int);

13 void printP(char[],int);

17 /****************************************************************

18 * Configuring the CGU

19 ****************************************************************

20 */

21 void CGU()

22 {

23 /* Enabling the main PLL. Output of PLL is 60MHz */

24 LPFIN=0x1; /* Select the clock source as the 12MHz crystal */

25 LPMSEL=4; /* Multiplication Factor */

26 LPPSEL=1; /* Division Factor */

27 LPPDN=0; /* Maintaining the reset condition- enabled */

29 while(!(LPLOCK & 1)){}

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Getting started with LPC288x

31 /* Selection stage- UART */

32 UARTSCR=0x1; /* Enables Side 1 of selection stage */

33 UARTFSR1=0x1; /* Select the clock source as the 12MHz crystal */

35 }

37 /****************************************************************

38 * Switching clocks between 60MHz and 32.768KHz osc. input

39 * Parameter 's' has a defined value.

40 * s=1-> Main PLL

41 * s=2-> 32.768KHz

42 ****************************************************************

43 */

44 void switch_clk(int s)

45 {

46 int temp;

47 int new_clk;

49 /* If s=1 then configure the UART for Main PLL else for the 32.768KHz crystal*/

50 if(s==1)

51 {

52 /* Set the new clock as the main PLL source. This value is used

53 * later while setting the Frequency select register

54 */

55 new_clk=0x8;

57 // Configuring UART for Main PLL

58 UARTRES=0x0;

59 UARTRES=0x1;

61 U0_FCR = 0x7;

62 U0_LCR = 0x83;

63 U0_DLL = 0x6a; /* Divider set to 6250 */

64 U0_DLM = 0x18;

65 U0_LCR = 0x3;

66 }

67 else

68 {

69 /* Set the new clock as the 32.768KHz. This value is used

70 * later while setting the Frequency select register

71 */

72 new_clk=0x0;

74 // Configuring UART for 32.768KHz osc

75 UARTRES=0x0;

76 UARTRES=0x1;

78 U0_FCR = 0x7;

79 U0_FDR= 0xF2;

80 U0_LCR = 0x83;

81 U0_DLL = 0x3; /* Divider set to 3 */

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Getting started with LPC288x

82 U0_LCR = 0x3;

83 }

85 /* Read the Switch status register to check

86 * which side of the stage is enabled

87 */

88 temp=UARTSSR;

90 if(temp & 1)

91 {

92 /* Set the clock on Side 2 */

93 UARTFSR2=new_clk;

94 /* Write to the Switch Configuration register */

95 UARTSCR=(temp & 0x3)^ 0x3;

96 /* Wait till the switch is complete*/

97 while(!(temp & 0x2))

98 {

99 temp=UARTSSR;

100 }

101 }

102 else

103 {

104 /* Set the clock on Side 1 */

105 UARTFSR1=new_clk;

106 /* Write to the Switch Configuration register */

107 UARTSCR=(temp & 0x3)^ 0x3;

108 /* Wait till the switch is complete */

109 while(!(temp & 0x1))

110 {

111 temp=UARTSSR;

112 }

113

114 }

115 }

116

117 /****************************************************************

118 * Function for printing characters on the Terminal program (PC).

119 * The function takes two parameters, a character array "a" and an integer "k"

120 * It prints the character array "a", "k"times

121 ****************************************************************

122 */

123 void printP(char a[],int k)

124 {

125 int i=0,j=0;

126

127 for(j=0;j<k;j++)

128 {

129 while(a[i])

130 {

131 U0_THR=a[i];

132 while(!(U0_LSR & TEMT)){}

Application note Rev. 01 — 8 January 2007 8 of 25

NXP Semiconductors AN10548

Getting started with LPC288x

133 i++;

134 }

135 U0_THR=CARRIAGE_RET;

136 U0_THR=LINE_FEED;

137 while(!(U0_LSR & TEMT)){}

138

139 i=0;

140 }

141

142

143 }

144

145 /****************************************************************

146 * MAIN

147 ****************************************************************

148 */

149 int main(void)

150 {

151 /* Characters arrays */

152 char lpc[]="LPC288x";

153 char a[]="+++++++++++++++++++++++++++++++++++++";

154 char b[]="-------------------------------------";

155 char uart_12[]="UART Running from 12MHz Oscillator";

156 char uart_pll[]="UART Running from Main PLL";

157 char uart_32[]="UART Running from 32.768KHz";

158

159

160 /* Configuring the CGU */

161 CGU();

162

163 /* UART Configuration to derive 600baud from the 12MHz main oscillator */

164 U0_FCR = 0x7;

165 U0_LCR = 0x83;

166 U0_DLL = 0xE2; /* Divider set to 1250 */

167 U0_DLM = 0x4;

168 U0_LCR = 0x03;

169

170 /* Printing characters */

171 printP(a,1);

172 printP(uart_12,1);

173 printP(lpc,5);

174 printP(b,1);

175

176 /* Continous switching is done between 60MHz and

177 * 32.768Khz

178 */

179 while(1)

180 {

181 /* Switching to Main PLL and configuring the UART dividers for the same*/

182 switch_clk(1);

183 /* Printing characters */

Application note Rev. 01 — 8 January 2007 9 of 25

NXP Semiconductors AN10548

Getting started with LPC288x

184 printP(uart_pll,1);

185 printP(lpc,5);

186 printP(b,1);

187

188 /* Switching to 32.768KHz and configuring the UART dividers for the same */

189 switch_clk(2);

190 /* Printing characters */

191 printP(uart_32,1);

192 printP(lpc,5);

193 printP(b,1);

194 }

195

196 }

See Fig 1 for sample output.

Fig 1. Sample output

Application note Rev. 01 — 8 January 2007 10 of 25

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