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C166 User's Guide
C166 Introduction Compiling Programs Language Extensions Preprocessor 
Advanced Programming Sections, Classes, and Groups 
Special Sections Locating Sections Customization Files Startup Code STARTUP.A66 START167.A66 START_V2.A66 START_V3.A66 Basic I/O Memory Allocation TRAPS.C Optimizer Optimizer Options General Optimizations 80C166-Specific Optimizations Global Register Coloring DPP Registers Stacks System Stack User Stack Stack Sizes System Stack Size User Stack Size XBUS Memory and Peripherals On-chip XRAM XBUS Peripherals Interfacing C to Assembler Function Parameters Function Return Values Using the SRC Directive Register Usage Example Routines TINY Model SMALL Model COMPACT Model MEDIUM Model LARGE Model Data Storage Formats Bit Variables 1-byte Scalars 2-byte Scalars 4-byte Scalars float Scalars float Errors double Scalars double Errors near Pointers far Pointers huge Pointers xhuge Pointers Absolute Memory Access Absolute Access Macros Linker Location Controls Debugging Error Messages Library Reference AppendixSTARTUP.A66
The STARTUP.A66 file contains the startup code for a C166 target program. Use this file for the C166 and GOLD derivatives of the C166 microcontroller family.
The startup code is executed immediately upon reset of the target system and performs the following operations in order:
- Initializes the SYSCON SFRs.
- 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.
STARTUP.A66 contains definitions that are used to configure the hardware of the 80C166 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: 0 for 256-word system stack 1 for 128-word system stack 2 for 64-word system stack 3 for 32-word system stack 4 for 512-word system stack (not for C166) 7 for user-defined system-stack size 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. |
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