Appendix B. Version Differences

This appendix lists an overview of major product enhancements and differences between the current version of the Cx51 compiler and previous versions. The current version contains all enhancements listed below:

Version 6.0 Differences B

EXTERNAL and SEGMENT limitations removed

The number of external symbols and segments per module are no longer limited to 256. This historical limitation was imposed by the old Intel Object File format.

First 256 characters of a variable name are significant

Now the first 256 characters of a variable name are significant. Previously, only the first 32 characters were significant.

Support for Philips 80C51MX and Dallas Contiguous Mode

Cx51 provides support for the Philips 80C51MX architecture and the Dallas Contiguous Mode that is available on the Dallas 390 and variants.

OMF2 directive and far memory type support

The OMF2 directive selects a new OMF file format that provides detailed symbol type checking across modules and supports up to 16MB code and xdata memory. This format is required when you use the STRING, VARBANKING, and XCROM directives.

STRING directive

Cx51 allows you to locate constant strings into const xdata or const far space which leaves more code space available for program code.

USERCLASS directive

Assigns user defined class names to compiler generated segments. Class names may be referenced by the LX51 linker to locate all segments with a specific class name.

VARBANING directive and far memory type support

Two new memory types, far and const far, and user configureable access routines provide support for up to 16MB extended code and xdata memory. The VARBANKING directive enables far memory type support.

XCROM directive

The XCROM directive locates constants into xdata ROM which frees code ROM space for program code.

Support for Analog Devices B2 series of MicroConverters

The B2 series of ADuC devices contains dual DPTR and an extended stack.

NOTE

Only the the PK51 Professional Developers Kit supports the OMF2 output file format, Philips 80C51MX, Dallas Contiguous Mode, and VARBANKING. These options are not available in the CA51 and DK51 packages.

B

Version 5 Differences

Optimize Level 7, 8, and 9

C51 offers three new optimizer levels. These new optimizations focus primarily on code density. Refer to “Optimizer” on page 157 for more information.

Directives for the dual DPTR support

C51 provides dual DPTR support for Atmel, Atmel WM, and, Philips with the directives MODA2 and MODP2.

data, pdata, xdata automatic variables overlayable in all memory models

C51 now overlays all data, pdata, and xdata automatic variables regardless of the selected memory model. In previous C51 versions, only automatic variables of the default memory type are overlaid. For example, C51 Version 5 did not overlay pdata or xdata variables if a function where compiled in the SMALL memory model.

The data type enum adjusts automatically 8 or 16 bits.

C51 now uses a char variable to represent an enum, if the enum range allows that.

modf, strtod, strtol, strtoul Library Functions

C51 now includes the ANSI standard library functions modf, strtod, strtol, strtoul

BROWSE, INCDIR, ONEREGBANK, RET_XSTK, and RET_PSTK Directives

C51 supports new directives for generating Browse Information, specifying include directives, optimizing interrupt code, and using the reentrant stack for return addresses. Refer to “Chapter 2. Compiling with the Cx51” on page 17 for more information.

Version 4 Differences

Byte Order of Floating-point Numbers

Floating-point numbers are now stored in the big endian order. Previous releases of the C51 compiler stored floating-point numbers in little endian format. Refer to “Floating-point Numbers” on page 179 for more information.

compiler now also checks for unused local variables, labels, and expressions. Refer to “WARNINGLEVEL” on page 85 for more information.

B