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C166: START167 AND BOOT167
QUESTION
I do not quite understand the files START167.A66 and BOOT167.A66.
Is BOOT.A66 used for the monitor and START167.A66 used for the final application ?
ANSWER
The BOOT167.A66 file is part of the boot loader used by the monitor.
Actually, the monitor consists of three files: BOOT*.A66, CONF*.INC, and INST*.A66.
CONF contains definitions for the stuff that gets initialized in the startup code for the monitor.
This code is in BOOT.
The CONF file contains definitions that are identical to those found in START167.A66.
So, to get a monitor working, the startup should be the same in CONF and in START167.
The INST file is the initialization for the monitor.
This includes things like the serial port used for communication with dScope and so on.
The START167.A66 file is the startup code that is executed immediately after reset by the CPU.
There‘s nothing much to add here.
If you have a monitor configuration that works, but your stand-alone program doesn‘t work,
you should compare the CONF*.INC from the monitor to the START167.A66 file for the stand-alone program.
There‘s probably a difference that prevents your program from working.
START167.A66
The START167.A66 file contains the startup code for the C161, C163, C164, C165, and C167 microcontrollers.
The startup code is executed immediately upon reset of the target system and performs the following operations in order:
- Initializes the SYSCON SFRs including BUSCON0.
- Initializes the ADDRSELx/BUSCONx SFRs (if configured).
- Reserves and initializes the hardware stack and stack overflow/underflow registers.
- Sets DPP0-DPP3 and CP for memory and register bank accesses.
- Reserves and initializes the user stack area and user stack pointer (R0).
- Clears data memory.
- Initializes explicitly initialized variables.
- Transfers control to the main C function.
START167.A66 contains definitions that are used to configure the hardware of the C16x and to setup the C runtime system.
The functions of the individual EQU statements are described below.
| Name | Definition |
|---|---|
| _ALECTL0 | ALE Lengthening Control Bit; see the C167 data sheet for description. |
| _BTYP0 or BYTP |
Defines the external bus configuration the CPU uses. The bus configuration is used only if BTYP_ENABLE is set to 1. |
| _BUSACT0 or BUSACT | Bus Active Control Bit. Default: 1 to enable the external bus. |
| _BYTDIS |
Byte High Enable pin control bit initialization value. Default: 0 for enabled. (This is the reset value of the CPU). To disable the BHE# output, set _BYTDIS to 1. |
| _CLREN |
System Clock Output Enable bit initialization value. Default: 0 to disable the CLKOUT output (this is also the reset value of the CPU.) To enable the CLKOUT output set _CLKEN to 1. |
| _MCTC0 or _MCTC |
Memory Cycle Time initialization value. Default: 1 for one memory wait state (MCTC = 0EH). Reset value of the CPU is 15 for 15 additional state times. |
| _MCTCn-_CSWENn |
Defines the bus characteristics for the address range specified with ADDRESSn and RANGEn. These values are used to set the BUSCON1-BUSCON4 registers. |
| _MTTC0 or MTTC |
Memory Tri-State Time initialization value. Default: 0 for 0.5 states; this is also the reset value of the CPU. To select 0 states for the Tri-State time, set _MTTC to 1. |
| _RDY_AS |
Synchronous / Asynchronous READY# input selection. Default: 0 for synchronous READY# input. |
| _RDYEN0 or RDYEN |
READY# Input Enable Control Bit. Default: 0 to disable the READY# input. |
| _ROMEN |
The Internal ROM Access Enable bit is read-only. Do not change this value. |
| _ROMS1 |
On-Chip ROM Segment-Mapping Control Bit. Default: 0 for on-chip ROM mapped to segment 0 (address range 0x0000-0xFFFF). Seg _ROMS1 to 1 for segment 1 (address range 0x10000-0x1FFFF). |
| _RWDC0 or RWDC |
Read/Write Signal Delay initialization value. Default: 1 for no delay (this is the typical value in most systems). Reset value of the CPU is 0 for 0.5 states delay time. |
| _SGTDIS |
Segmentation Disable Control Bit initialization value. The segmentation is disabled for the TINY memory model; in all other memory models it is enabled. Do not change the definition of _SGTDIS. |
| _WRCFG |
Write Configuration Control Bit. Default: 0 for normal configuration of WR# and BHE# outputs. |
| _XRAMEN |
XRAM Enable Control Bit. Default: 0 to disable access to XRAM area. External bus accesses are generated in the XRAM area. |
| ADDRESS1-ADDRESS4 |
Define the start address of the Chip Select 1-4 output (CS1#-CS4#). This value is used to set the ADDRSEL1-ADDRSEL4 register. |
| BTYP_ENABLE |
Allow software to modify BTYP and change the bus mode. By default, this is disabled and the bus type is set by the hardware pins of the C16x/ST10. To enable the external bus configuration, set BTYP_ENABLE = 1. |
| BUSCON1-BUSCON4 |
Initialization for BUSCON1/ADDRSEL1-BUSCON4/ADDRSEL4 registers. Set BUSCON1 = 1 to initialize BUSCON1/ADDRSEL1. |
| CLR_MEMORY |
Memory Zero Initialization of RAM areas. Default: enable the memory zero initialization of RAM area. To disable the memory zero initialization, set CLR_MEMORY = 1. This reduces the startup code size. |
| DPPUSE |
Allow re-assignment of DPP registers. Default: 1 to support the L166 DPPUSE directive. To disable the DPP re-assignment, set DPPUSE = 0. This reduces the startup code size. |
| EXT_RAM |
External RAM Write-Access Enable (P3.13 = WR-Pin) initialization value. The default value enables the external RAM access. To disable external RAM, remove the statement $SET (EXT_RAM). |
| INIT_VARS |
Variable Initialization of explicitly initialized variables (variables are to be defined as static or declared at file level). Default: initialize variables. To disable the variable initialization, set INIT_VARS = 0. This reduces the startup code size. |
| RANGE1-RANGE4 |
Define the address range of the Chip Select 1-4 output (CS1#-CS4#). This value is used to set the ADDRSEL1-ADDRSEL4 register. |
| SSTSZ |
Set the system stack space, if you selected 7 for the STK_SIZE. |
| STK_SIZE |
STK_SIZE: Maximum System Stack Size selection initialization value. Default value is 0 for 256-word stack size. Set STK_SIZE to the following values for other stack sizes:
If you select 7, the system-stack size is defined with the SSTSZ variable. |
| USTSZ |
Set the user stack space. The user stack is used for automatic variables. |
| WATCHDOG |
Hardware Watchdog control. Default: disable the hardware watchdog. To enable the watchdog set WATCHDOG = 1. |
C166: PURPOSE OF START167.A66
QUESTION
What is the purpose of the START167.A66 file? It seems to configure the memory arrangements of the device. If that is the case, when is it executed?
ANSWER
START167.A66 contains the startup code for the C167 derivative devices. It executes immediately upon reset of the device and optionally performs the following operations in order:
- Initializes the SYSCON SFR registers (and BUSCON0 for the C167).
- Initializes the ADDRSELx and BUSCONx SFR registers to configure memory access.
- Reserves and initializes the hardware stack and the stack underflow and overflow registers.
- Sets up DPP0 to DPP3 and CP for memory and registerbank access.
- Reserves and initializes the user stack area and the user stack pointer (R0).
- Clears data memory.
- Initializes variables that were explicitly initialized.
- Calls the main function.
If you are using the monitor, then the monitor contains it‘s own startup code that performs most of these operations. Once it has been completed, the startup code in your own application has no effect on the configuration of the device.
C166: START167.A66 FOR EVALUATION BOARDS
QUESTION
I have a Phytec KC167CR evaluation board and a simple IO port example to demonstrate the board. I use the default START167.A66 provided by the Keil C166 compiler. The program does not run on the KC167CR board. What could be wrong?
ANSWER
The purpose of the START167.A66 file is to configure specific hardware conditions of the C16X device specifically for the target hardware. In this case the target hardware is the Phytec KC167CR evaluation board. Therefore, you must have the specific Phytec provided START167.A66 file for the KC167CR.
The START167.A66 contains the startup code for the C167 derivative devices. It is executed immediately upon reset of the device and optionally performs the following operations in order:
- Initializes the SYSCON SFR registers (and BUSCON0 for the C167)
- Initializes the ADDRSELx and BUSCONx SFR registers to configure memory access
- Reserves and initializes the hardware stack and the stack underflow and overflow registers
- Sets up DPP0 to DPP3 and CP for memory and registerbank access
- Reserves and initializes the user stack area and the user stack pointer (R0)
- Clears data memory
- Initializes variables that were explicitly initialized
- Calls the main function
If you are using the monitor, then the monitor contains it‘s own startup code that performs most of these operations. Once it has been completed, the startup code in your own application has no effect on the configuration of the device.
The C:\Keil\C166\EXAMPLES\BOARDS directory has examples and the appropriate START167.A66 files for popular C16X evaluation boards.