AN131
P OR TING C ONSIDERATIONS FROM ‘ F 0 2 X TO ‘ F 1 2 X
Relevant Devices
Clocking
This application note applies to the following devices:
The main differences in clocking between the
C8051F02x series and the C8051F12x series
include an on-chip calibrated 24.5 MHz internal
oscillator and a phase-locked loop (PLL). When
porting code, be aware that the OSCICN register
definition has changed and a new register, CLKSEL, has been added to accommodate the increased
clocking flexibility.
C8051F020, C8051F021, C8051F022, C8051F023,
C8051F120, C8051F121, C8051F122, C8051F123,
C8051F124, C8051F125, C8051F126, and
C8051F127.
Introduction
The C8051F12x family has 128K of FLASH,
8.25K of RAM, and is capable of operating at
speeds up to 100MHz. This family is pin compati- The 24.5 MHz Internal Oscillator
ble with the C8051F02x series, but due to added The C8051F12x series has a calibrated
flexibility and functionality, is not code compati- 24.5 MHz (+/- 2%) internal oscillator, instead of
ble.
the 16 MHz (+/- 20%) internal oscillator on the
C8051F02x. On reset, the system starts operating at
This application note discusses differences between a frequency of approximately 3 MHz instead of
the C8051F12x series and the C8051F02x series. 2 MHz.
The main topics include clocking, SFR paging,
code banking, and caching. Example initialization Using the PLL to achieve
routines for the C8051F12x series and a checklist
to use when porting a project from a C8051F02x to operating frequencies up to
a C8051F12x device are included at the end of this 100 MHz
note.
Operating ‘F12x devices at frequencies greater
than 30 MHz is accomplished by using the PLL to
multiply a lower frequency oscillator source.
Key Points
•
•
•
The C8051F12x series is pin compatible with
the C8051F02x series but is not code compatible.
Most of the new features in the C8051F12x
series, such as the instruction cache and code
banking registers, may be left at their default
settings.
The ‘F12x devices implement ‘SFR Paging’.
To correctly read or write to an SFR register,
the SFRPAGE register must be set to the
correct SFR page.
Rev. 1.3 12/03
The input frequency range for the PLL is 5 to
30 MHz and can be derived from the internal or
external oscillator. Given a stable input signal, the
PLL output can have a wide range of frequencies
based on the values of PLL0MUL and PLL0DIV.
Keep in mind that the input clock signal is divided
by PLL0DIV before it is fed to the phase detector.
The phase detector input must be between 5 and
30 MHz. The maximum output frequency of the
PLL is limited by the maximum operating frequency of the device.
Copyright © 2003 by Silicon Laboratories
AN131
AN131
Figure 1. SFR Page Names
Example code showing how to initialize the PLL is
included at the end of this note. Please refer to the
Oscillators section of the C8051F12x datasheet for
step-by-step instructions for initializing the PLL.
SFR Page Names
SFR Paging
The C8051F12x series implements a ‘paged’ SFR
scheme which greatly expands the number of available SFR addresses. This SFR address expansion
provides support for more peripherals and gives the
programmer added flexibility. For example, Port 4
through Port 7 now occupy bit-addressable SFR
locations.
Reading and Writing to SFR
Registers
SFR Page
Number
CPT0_PAGE
UART1_PAGE
TMR3_PAGE
DAC1_PAGE
0x01
CPT1_PAGE
ADC2_PAGE
TMR4_PAGE
0x02
CONFIG_PAGE
PLL0_PAGE
0x0F
SFR Paging and Interrupts
By default, SFR page switching is handled automatically by hardware when an interrupt occurs.
Upon entry into an interrupt service routine (ISR),
the SFRPAGE register will automatically switch to
the SFR page containing the flag bit that caused the
interrupt. Upon exit of the ISR, the SFR page is
automatically restored to the SFR page in use prior
to the interrupt.
To correctly read or write to an SFR, the SFRPAGE
register must be set to the correct SFR page. The
SFRPAGE register is accessible from all SFR
pages. When changing SFR pages, it is recommended to use the named constants in Figure 1
instead of assigning the actual SFR page number.
These are defined in the supplied ‘C8051F120.h’
and ‘C8051F120.inc’ files. This enhances code
readability and reduces the porting effort to future For more information on SFR paging, please see
platforms.
the CIP-51 section of the C8051F12x datasheet.
Figure 1. SFR Page Names
SFR Page Names
LEGACY_PAGE
TIMER01_PAGE
UART0_PAGE
SPI0_PAGE
EMI0_PAGE
ADC0_PAGE
SMB0_PAGE
TMR2_PAGE
DAC0_PAGE
PCA0_PAGE
2
SFR Page
Number
0x00
Rev. 1.3
AN131
Code Banking
changes the COBANK bits, it should restore them
prior to ISR exit. The PSBANK register is not
The C8051F12x series supports code banking for restored by hardware and should be managed by
projects requiring greater than 64KB of FLASH. software.
All code bank switching is handled by writing to
the PSBANK register. Projects smaller than 64KB Project-Managed Bank
can leave the PSBANK register at its default setSwitching
ting which provides a 64KB linear address space.
Allowing the linker to manage code banking is a
When code banking is used, the common area must for projects that have more than 64KB of exe(FLASH addresses between 0x0000 to 0x7FFF) is cutable program code. It allows functions in one
always available regardless of the PSBANK regis- bank to call functions located in another bank withter. The address space from 0x8000 to 0xFFFF can out the programmer having to worry about bank
be mapped to one of 4 physical 32KB banks of switching. There is a restriction, however. Constant
FLASH, depending on the value of PSBANK. code variables and tables must be located in the
Please see the FLASH and CIP-51 sections of the common area or in the bank containing the function
C8051F12x datasheet for more detailed informa- which accesses them. For more information on this
tion on the code banking architecture.
topic and for step-by-step instructions on how to
set up a code-banked project, please refer to
For larger projects, the user has the option of manu- AN130 on the Silicon Labs website.
ally handling the bank switching in software or setting up a code banked project and allowing the
linker to manage the bank switching. The advan- Caching
tages and disadvantages of both methods are dis- The ‘F12x family of devices possess a branch tarcussed below.
get buffer and a pre-fetch engine which provide
optimal performance for a broad range of circumstances. In most applications, the cache control registers should be left in their reset states. Please refer
to the C8051F12x datasheet for more information
User-managed bank switching is useful for projects on the cache controller.
that have less than 64KB of executable code but
need to store large amounts of data in FLASH. In
this situation, the common area and Bank 1 are Interrupt Vector Table
used for program memory while Bank 2 and
The interrupt vector table in the ‘F12x is different
Bank 3 are used for data storage. The project does
from the ‘F02x interrupt vector table. External
not need to be set up for code banking.
Interrupt 6, External Interrupt 7, and the External
Crystal OSC Ready interrupts have been removed.
Bank selection for constant data (accessed via
The ADC2 Window Comparator interrupt has been
MOVC and MOVX instructions) is handled indeadded as interrupt 17 (0x008B) and the ADC1 End
pendently of bank selection for instruction fetches
of Conversion interrupt has been renamed to ADC2
(normal code execution). The IFBANK bits, which
End of Conversion and moved to interrupt 18
control the instruction fetch operations, should be
left at their reset values, targeting Bank 1. The
COBANK bits, which control constant operations,
should be set to select the desired bank before reading, writing, or erasing FLASH. If an interrupt
User-Managed Bank Switching
for Data Intensive Projects
Rev. 1.3
3
AN131
(0x0093). The interrupt vector changes are outlined C8051F12x devices. Both types of modifications
in the tables below.
are discussed below, sorted by peripheral.
Figure 2. Interrupts Added to the
‘F12x
Interrupt
Source
Interrupt
Vector
Priority
ADC2 Window
Comparator
0x008B
17
Analog-to-Digital Converter
(ADC)
Both the 12-bit and 10-bit versions of ADC0 are
identical to ADC0 on the ‘F02x devices. ADC1 (8bit 500 ksps) has been renamed to ADC2 on the
‘F12x. ADC2 now supports differential mode in
addition to single-ended mode and has its own Programmable Window Comparator. Also, the
CNVSTR signal has been renamed to CNVSTR0.
Please refer to the C8051F12x datasheet for ADC2
configuration information. Note that SFRPAGE
should be set to ADC0_PAGE or ADC2_PAGE
when reading or writing the corresponding ADC
registers.
Figure 3. Interrupts No Longer
Present in the ‘F12x
Interrupt
Source
Interrupt
Vector
Priority
External
Interrupt 6
0x0093
18
External
Interrupt 7
0x009B
19
External
Crystal OSC
Ready
0x00AB
21
Digital-to-Analog Converter
(DAC)
Both DAC0 and DAC1 on the ‘F12x are identical
to DAC0 and DAC1 on the ‘F02x. However, be
sure to set the SFRPAGE to DAC0_PAGE or
DAC1_PAGE before reading or writing to any
DAC registers.
Figure 4. Interrupts That Have
Changed Locations in the ‘F12x
Interrupt
Source
Interrupt
Vector
Priority
ADC1 End of
Conversion
is now
ADC2 End of
Conversion
0x008B
17
0x0093
18
Voltage Reference (VREF)
VREF1 on the ‘F02x has been renamed to VREF2
on the ‘F12x. Pin locations are unchanged. Note
that SFRPAGE should be set to LEGACY_PAGE
before any reads or writes to REF0CN.
Comparators
Device Comparison and
Porting Checklist
When porting a project from a C8051F02x device
to a C8051F12x device, some code modifications
are required and others are made to fully utilize the
enhanced flexibility and performance of the
4
The comparators on the ‘F12x have been enhanced
over the equivalent ‘F02x comparators with a new
speed/power selection capability. As a result, two
new registers, CPT0MD and CPT1MD, have been
added to accommodate this new feature. These registers give the user the option of putting
comparator 0 and comparator 1 in a low power
mode. The reset value for these registers leaves the
speed and power consumption of ‘F12x compara-
Rev. 1.3
AN131
tors equivalent to the speed and power consumption of the ‘F02x comparators. Note that SFRPAGE
should be set to CPT0_PAGE or CPT1_PAGE
when reading or writing comparator registers.
Reset Sources
Forcing a power-on reset via software in the ‘F12x
is accomplished by writing a ‘1’ to PINRSF (bit 0
in the RSTSRC register) instead of PORSF (bit 1 in
the RSTSRC register) as in the ‘F02x. PORSF in
the ‘F12x has been changed from read/write to read
only.
The instruction prefetch engine must be enabled in
order to disable the watchdog timer. The instruction
prefetch engine is enabled by default upon reset.
P74OUT register has been removed. Note that
SFRPAGE should be set to CONFIG_PAGE when
reading or writing to Port 4 through Port 7 and the
port input and output mode (PnMDIN and PnMDOUT) registers.
The CEX5 and CNVSTR2 signals have been added
as Crossbar inputs. The CNVSTR signal has been
renamed to CNVSTR0. If the application does not
use any of the newly added or renamed signals,
then the Crossbar configuration code will not need
modification. Note that SFRPAGE should be set to
CONFIG_PAGE before reading or writing to crossbar registers.
System Management Bus/I2C
Bus (SMBUS0)
Note that SFRPAGE should be set to LEGA- The formula for calculating SMB0CR has changed
CY_PAGE before any reads or writes to RSTSRC. on the ‘F12x. Please refer to the System Management Bus section of the C8051F12x datasheet for
Oscillators
more information about SMBUS0. Note that
Please see the “Clocking” section of this docu- SFRPAGE should be set to SMB0_PAGE before
any reads or writes to SMBUS0 registers.
ment.
FLASH Memory
Enhanced Serial Peripheral
Interface (SPI0)
Please see the “Code Banking” section of this docThe ‘F12x series features an enhanced Serial
ument.
Peripheral Interface. The enhanced SPI0 supports
double buffered transmits and multi-byte transacExternal Memory Interface
tions when in slave mode. Also, it can now operate
(EMIF)
in 3-wire or 4-wire mode making the NSS signal
The external memory interface on the ‘F12x is optional. The SPI0 configuration registers have
identical to the one on the ‘F02x. However, changed on the ‘F12x. For more information on the
because the ‘F12x devices can operate significantly enhanced SPI0, please refer to the C8051F12x
faster than the ‘F02x devices, be sure to check the datasheet. Note that SFRPAGE should be set to
timing requirements for devices on the bus. Note SPI0_PAGE before any reads or writes to SPI0 regthat SFRPAGE should be set to LEGACY_PAGE isters.
before any reads or writes to EMIF registers.
UART
Port Input/Output
For UART0 on the ‘F12x, timer selection for baud
Port 4 through Port 7 now occupy bit addressable rate generation has been moved to the newly added
SFR locations on the ‘F12x. Separate PnMDOUT SSTA0 register. UART0 now supports using
registers have been added for each port and the
Rev. 1.3
5
AN131
Timer 1, Timer 2, Timer 3, or Timer 4 as its baud PCA0_PAGE before any reads or writes to PCA0
registers.
rate source.
UART1 no longer requires an external crystal for JTAG
baud rate generation when used with the calibrated
24.5 MHz internal oscillator. Due to these changes, The JTAG device ID has changed for the ‘F12x
the baud rate calculation equations have changed. series. See the JTAG section of the ‘F12x datasheet
UART1 supports using Timer 1 as its baud rate for details on the JTAG interface.
source. Hardware address decoding, synchronous
mode, and fixed baud rate mode are not supported
by UART1.
Note that SFRPAGE should be set to
UART0_PAGE or UART1 PAGE before accessing
any UART registers. Be aware that the timer registers may not appear on the same page as the UART
registers. SFRPAGE should also be set to the
proper UART page prior to calls to ‘printf’ or to
other input/output stream functions to direct the
operations to UART0 or UART1.
Timers
For Timer 0 and Timer 1, an additional prescaler
has been added which allows them to be clocked
from SYSCLK, SYSCLK divided by 4, SYSCLK
divided by 12, or SYSCLK divided by 48. Timer 0
and Timer 1 SFRs are located on the “TIMER01_PAGE” SFR page.
Timer 2, Timer 3, and Timer 4 on the ‘F12x are
enhanced forms of the equivalent ‘F02x timers.
These new timers support output toggle mode, and
down count capability. For more information on
these timers, please refer to the C8051F12x datasheet. Note that SFRPAGE should be set to
TMR2_PAGE, TMR3_PAGE, or TMR4_PAGE
before any reads or writes to Timer 2, 3, or 4 registers, respectively.
Programmable Counter Array
(PCA)
In the ‘F12x, an additional capture/compare module was added for a total of 6 capture/compare
modules. Note that SFRPAGE should be set to
6
Rev. 1.3
AN131
Software Examples
Example 1
//----------------------------------------------------------------------------// F12x_INIT_1.c
//----------------------------------------------------------------------------// Copyright 2002 Cygnal Integrated Products, Inc.
//
// AUTH: FB
// DATE: 19 SEP 02
//
// This file contains example initialization routines for the C8051F12x series
// of devices.
//
// This program uses the the 24.5 MHz internal oscillator multiplied by two
// for an effective SYSCLK of 49 MHz. This program also initializes and uses
// UART1 at <BAUDRATE> bits per second.
//
//
// Target: C8051F12x
// Tool chain: KEIL C51 6.03 / KEIL EVAL C51
//
//----------------------------------------------------------------------------// Includes
//----------------------------------------------------------------------------#include <c8051f120.h>
// SFR declarations
#include <stdio.h>
// printf() and getchar()
//----------------------------------------------------------------------------// 16-bit SFR Definitions for 'F12x
//----------------------------------------------------------------------------sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
DP
ADC0
ADC0GT
ADC0LT
RCAP2
RCAP3
RCAP4
TMR2
TMR3
TMR4
DAC0
DAC1
PCA0CP5
PCA0CP2
PCA0CP3
PCA0CP4
PCA0
PCA0CP0
PCA0CP1
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
0x82;
0xbe;
0xc4;
0xc6;
0xca;
0xca;
0xca;
0xcc;
0xcc;
0xcc;
0xd2;
0xd2;
0xe1;
0xe9;
0xeb;
0xed;
0xf9;
0xfb;
0xfd;
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
data pointer
ADC0 data
ADC0 greater than window
ADC0 less than window
Timer2 capture/reload
Timer3 capture/reload
Timer4 capture/reload
Timer2
Timer3
Timer4
DAC0 data
DAC1 data
PCA0 Module 5 capture
PCA0 Module 2 capture
PCA0 Module 3 capture
PCA0 Module 4 capture
PCA0 counter
PCA0 Module 0 capture
PCA0 Module 1 capture
Rev. 1.3
7
AN131
//----------------------------------------------------------------------------// Global CONSTANTS
//----------------------------------------------------------------------------#define TRUE
1
#define FALSE
0
#define INTCLK
#define SYSCLK
#define BAUDRATE
24500000
49000000
115200
sbit LED = P1^6;
sbit SW2 = P3^7;
// Internal oscillator frequency in Hz
// Output of PLL derived from (INTCLK*2)
// Baud rate of UART in bps
// LED='1' means ON
// SW2='0' means switch pressed
//----------------------------------------------------------------------------// Function PROTOTYPES
//----------------------------------------------------------------------------void main(void);
void SYSCLK_Init(void);
void PORT_Init(void);
void UART1_Init (void);
//----------------------------------------------------------------------------// MAIN Routine
//----------------------------------------------------------------------------void main (void)
{
WDTCN = 0xde;
WDTCN = 0xad;
// disable watchdog timer
PORT_Init ();
SYSCLK_Init ();
UART1_Init ();
// initialize crossbar and GPIO
// initialize oscillator
// initialize UART1
SFRPAGE = UART1_PAGE;
printf("Hello\n");
// Direct printf output to UART1
// Print a string
while(1);
}
//----------------------------------------------------------------------------// Initialization Routines
//----------------------------------------------------------------------------//----------------------------------------------------------------------------// SYSCLK_Init
//----------------------------------------------------------------------------//
// This routine initializes the system clock to use the internal oscillator
8
Rev. 1.3
AN131
// at 24.5 MHz multiplied by two using the PLL.
//
void SYSCLK_Init (void)
{
int i;
// software timer
char SFRPAGE_SAVE = SFRPAGE;
// Save Current SFR page
SFRPAGE = CONFIG_PAGE;
// set SFR page
OSCICN = 0x83;
// set internal oscillator to run
// at its maximum frequency
CLKSEL = 0x00;
// Select the internal osc. as
// the SYSCLK source
//Turn on the PLL and increase the system clock by a factor of M/N = 2
SFRPAGE = CONFIG_PAGE;
PLL0CN = 0x00;
SFRPAGE = LEGACY_PAGE;
FLSCL
= 0x10;
SFRPAGE =
PLL0CN |=
PLL0DIV =
PLL0FLT =
CONFIG_PAGE;
0x01;
0x01;
0x01;
// Set internal osc. as PLL source
// Set FLASH read time for 50MHz clk
// or less
PLL0MUL = 0x02;
//
//
//
//
//
//
Enable Power to PLL
Set Pre-divide value to N (N = 1)
Set the PLL filter register for
a reference clock from 19 - 30 MHz
and an output clock from 45 - 80 MHz
Multiply SYSCLK by M (M = 2)
for (i=0; i < 256; i++) ;
PLL0CN |= 0x02;
while(!(PLL0CN & 0x10));
CLKSEL = 0x02;
//
//
//
//
Wait at least 5us
Enable the PLL
Wait until PLL frequency is locked
Select PLL as SYSCLK source
SFRPAGE = SFRPAGE_SAVE;
// Restore SFR page
}
//----------------------------------------------------------------------------// PORT_Init
//----------------------------------------------------------------------------//
// This routine configures the crossbar and GPIO ports.
//
void PORT_Init (void)
{
char SFRPAGE_SAVE = SFRPAGE;
// Save Current SFR page
SFRPAGE = CONFIG_PAGE;
XBR0
XBR1
// set SFR page
= 0x00;
= 0x00;
Rev. 1.3
9
AN131
XBR2
= 0x44;
// Enable crossbar and weak pull-up
// Enable UART1
P0MDOUT |= 0x01;
P1MDOUT |= 0x40;
// Set TX1 pin to push-pull
// Set P1.6(LED) to push-pull
SFRPAGE = SFRPAGE_SAVE;
// Restore SFR page
}
//----------------------------------------------------------------------------// UART1_Init
//----------------------------------------------------------------------------//
// Configure the UART1 using Timer1, for <baudrate> and 8-N-1.
//
void UART1_Init (void)
{
char SFRPAGE_SAVE = SFRPAGE;
// Save Current SFR page
SFRPAGE = UART1_PAGE;
SCON1
= 0x10;
// SCON1: mode 0, 8-bit UART, enable RX
SFRPAGE = TIMER01_PAGE;
TMOD
&= ~0xF0;
TMOD
|= 0x20;
// TMOD: timer 1, mode 2, 8-bit reload
if (SYSCLK/BAUDRATE/2/256 < 1) {
TH1 = -(SYSCLK/BAUDRATE/2);
CKCON |= 0x10;
// T1M =
} else if (SYSCLK/BAUDRATE/2/256 < 4) {
TH1 = -(SYSCLK/BAUDRATE/2/4);
CKCON &= ~0x13;
// Clear
CKCON |= 0x01;
// T1M =
} else if (SYSCLK/BAUDRATE/2/256 < 12) {
TH1 = -(SYSCLK/BAUDRATE/2/12);
CKCON &= ~0x13;
// T1M =
} else {
TH1 = -(SYSCLK/BAUDRATE/2/48);
CKCON &= ~0x13;
// Clear
CKCON |= 0x02;
// T1M =
}
all T1 related bits
0; SCA1:0 = 01
0; SCA1:0 = 00
all T1 related bits
0; SCA1:0 = 10
TL1 = TH1;
TR1 = 1;
// initialize Timer1
// start Timer1
SFRPAGE = UART1_PAGE;
TI1 = 1;
// Indicate TX1 ready
SFRPAGE = SFRPAGE_SAVE;
// Restore SFR page
}
10
1; SCA1:0 = xx
Rev. 1.3
AN131
Example 2
//----------------------------------------------------------------------------// F12x_INIT_2.c
//----------------------------------------------------------------------------// Copyright 2002 Cygnal Integrated Products, Inc.
//
// AUTH: FB
// DATE: 19 SEP 02
//
// This file contains example initialization routines for the C8051F12x series
// of devices.
//
// This program uses a 22.1184 Mhz crystal oscillator multiplied by (9/4)
// for an effective SYSCLK of 49.7664 Mhz. This program also initializes and
// uses UART0 at <BAUDRATE> bits per second.
//
//
// Target: C8051F12x
// Tool chain: KEIL C51 6.03 / KEIL EVAL C51
//
//----------------------------------------------------------------------------// Includes
//----------------------------------------------------------------------------#include <c8051f120.h>
// SFR declarations
#include <stdio.h>
// printf() and getchar()
//----------------------------------------------------------------------------// 16-bit SFR Definitions for 'F12x
//----------------------------------------------------------------------------sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
sfr16
DP
ADC0
ADC0GT
ADC0LT
RCAP2
RCAP3
RCAP4
TMR2
TMR3
TMR4
DAC0
DAC1
PCA0CP5
PCA0CP2
PCA0CP3
PCA0CP4
PCA0
PCA0CP0
PCA0CP1
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
0x82;
0xbe;
0xc4;
0xc6;
0xca;
0xca;
0xca;
0xcc;
0xcc;
0xcc;
0xd2;
0xd2;
0xe1;
0xe9;
0xeb;
0xed;
0xf9;
0xfb;
0xfd;
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
data pointer
ADC0 data
ADC0 greater than window
ADC0 less than window
Timer2 capture/reload
Timer3 capture/reload
Timer4 capture/reload
Timer2
Timer3
Timer4
DAC0 data
DAC1 data
PCA0 Module 5 capture
PCA0 Module 2 capture
PCA0 Module 3 capture
PCA0 Module 4 capture
PCA0 counter
PCA0 Module 0 capture
PCA0 Module 1 capture
//----------------------------------------------------------------------------// Global CONSTANTS
Rev. 1.3
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AN131
//----------------------------------------------------------------------------#define TRUE
1
#define FALSE
0
#define EXTCLK
#define SYSCLK
22118400
49760000
// External oscillator frequency in Hz
// Output of PLL derived from
// (EXTCLK*9/4)
#define BAUDRATE
115200
//
//
//
//
//
sbit LED = P1^6;
sbit SW2 = P3^7;
Baud rate of UART in bps
Note: The minimum standard baud rate
supported by the UART0_Init routine
in this file is 19,200 bps when
SYSCLK = 49.76MHz.
// LED='1' means ON
// SW2='0' means switch pressed
//----------------------------------------------------------------------------// Function PROTOTYPES
//----------------------------------------------------------------------------void main(void);
void SYSCLK_Init(void);
void PORT_Init(void);
void UART0_Init (void);
//----------------------------------------------------------------------------// MAIN Routine
//----------------------------------------------------------------------------void main (void)
{
WDTCN = 0xde;
WDTCN = 0xad;
// disable watchdog timer
PORT_Init ();
SYSCLK_Init ();
UART0_Init ();
// initialize crossbar and GPIO
// initialize oscillator
// initialize UART0
SFRPAGE = UART0_PAGE;
printf("Hello\n");
// Direct printf output to UART0
// Print a string
while(1);
}
//----------------------------------------------------------------------------// Initialization Routines
//----------------------------------------------------------------------------//----------------------------------------------------------------------------// SYSCLK_Init
12
Rev. 1.3
AN131
//----------------------------------------------------------------------------//
// This routine initializes the system clock to use an external 22.1184 MHz
// crystal oscillator multiplied by a factor of 9/4 using the PLL as its
// clock source. The resulting frequency is 22.1184 MHz * 9/4 = 49.7664 MHz
//
void SYSCLK_Init (void)
{
int i;
// delay counter
char SFRPAGE_SAVE = SFRPAGE;
// Save Current SFR page
SFRPAGE = CONFIG_PAGE;
// set SFR page
OSCXCN = 0x67;
// start external oscillator with
// 22.1184MHz crystal
for (i=0; i < 256; i++) ;
// Wait for osc. to start up
while (!(OSCXCN & 0x80)) ;
// Wait for crystal osc. to settle
CLKSEL = 0x01;
// Select the external osc. as
// the SYSCLK source
OSCICN = 0x00;
// Disable the internal osc.
//Turn on the PLL and increase the system clock by a factor of M/N = 9/4
SFRPAGE = CONFIG_PAGE;
PLL0CN = 0x04;
SFRPAGE = LEGACY_PAGE;
FLSCL
= 0x10;
SFRPAGE =
PLL0CN |=
PLL0DIV =
PLL0FLT =
CONFIG_PAGE;
0x01;
0x04;
0x01;
// Set PLL source as external osc.
// Set FLASH read time for 50MHz clk
// or less
PLL0MUL = 0x09;
//
//
//
//
//
//
Enable Power to PLL
Set Pre-divide value to N (N = 4)
Set the PLL filter register for
a reference clock from 19 - 30 MHz
and an output clock from 45 - 80 MHz
Multiply SYSCLK by M (M = 9)
for (i=0; i < 256; i++) ;
PLL0CN |= 0x02;
while(!(PLL0CN & 0x10));
CLKSEL = 0x02;
//
//
//
//
Wait at least 5us
Enable the PLL
Wait until PLL frequency is locked
Select PLL as SYSCLK source
SFRPAGE = SFRPAGE_SAVE;
// Restore SFR page
}
//----------------------------------------------------------------------------// PORT_Init
//----------------------------------------------------------------------------//
Rev. 1.3
13
AN131
// This routine configures the crossbar and GPIO ports.
//
void PORT_Init (void)
{
char SFRPAGE_SAVE = SFRPAGE;
// Save Current SFR page
SFRPAGE = CONFIG_PAGE;
// set SFR page
XBR0
XBR1
XBR2
// Enable UART0
= 0x04;
= 0x00;
= 0x40;
// Enable crossbar and weak pull-up
P0MDOUT |= 0x01;
P1MDOUT |= 0x40;
// Set TX0 pin to push-pull
// Set P1.6(LED) to push-pull
SFRPAGE = SFRPAGE_SAVE;
// Restore SFR page
}
//----------------------------------------------------------------------------// UART0_Init
//----------------------------------------------------------------------------//
// Configure the UART0 using Timer1, for <baudrate> and 8-N-1. In order to
// increase the clocking flexibility of Timer0, Timer1 is configured to count
// SYSCLKs.
//
// To use this routine SYSCLK/BAUDRATE/16 must be less than 256. For example,
// if SYSCLK = 50 MHz, the lowest standard baud rate supported by this
// routine is 19,200 bps.
//
void UART0_Init (void)
{
char SFRPAGE_SAVE = SFRPAGE;
// Save Current SFR page
SFRPAGE = UART0_PAGE;
SCON0
SSTA0
= 0x50;
= 0x10;
SFRPAGE = TIMER01_PAGE;
TMOD
&= ~0xF0;
TMOD
|= 0x20;
14
// SCON0: mode 0, 8-bit UART, enable RX
// Timer 1 generates UART0 baud rate and
// UART0 baud rate divide by two disabled
// TMOD: timer 1, mode 2, 8-bit reload
TH1 = -(SYSCLK/BAUDRATE/16);
//
//
//
//
Set the Timer1 reload value
When using a low baud rate, this equation
should be checked to ensure that the
reload value will fit in 8-bits.
CKCON |= 0x10;
// T1M = 1; SCA1:0 = xx
TL1 = TH1;
TR1 = 1;
// initialize Timer1
// start Timer1
Rev. 1.3
AN131
SFRPAGE = UART0_PAGE;
TI0 = 1;
// Indicate TX0 ready
SFRPAGE = SFRPAGE_SAVE;
// Restore SFR page
}
Rev. 1.3
15
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