Technical White Paper BIOS Development Group
General Software, Inc.
www.gensw.com Approved for Public Release
Building on the AMD Élan ™ SC400
Reference Design with Embedded BIOS ™
Introduction
The AMD Élan SC400 Evaluation Board provides a rich hardware testbed for mobile, handheld, embedded, and consumer electronics applications. With its built-in support for matrix keyboards, LCD displays, PC cards, multiple banks of Flash memory, power management, VL bus video, ISA, and on-board UART and parallel ports, the board makes it possible to exercise these features before the OEM’s actual hardware becomes available. The platform boots with General Software’s Embedded BIOS™ firmware and can support application programming in DOS, Win- dows CE, Windows 95/98, Windows NT, QNX, and other embedded operating systems.
The General Software Embedded BIOSAdaptation Kit for the SC400 provides industry-standard BIOS core software with the special embedded support for products built around this design.
Using its rule-based expert system, BIOStart™, to help configure the BIOS, an OEM can select from a range of over 400 configuration options to produce a perfect-fit BIOS for an application.
At the same time, the BIOS adaptation remains compliant with PC BIOS industry standards as required by operating systems and application software.
The special “embedded” features provided by the Embedded BIOS firmware makes practical use of the embedded features of the SC400 and makes it possible to prototype handheld and mobile designs. The Resident Flash Disk (RFD), Flash programming services, built-in BIOS debugger (Flash, Super I/O, and chipset-aware), Windows CE Loader, Manufacturing Mode host link, Burn-In Diagnostics in Setup, Console Redirection over serial links, LCD display driver, VL bus video driver, PC card driver (ATA and linear flash cards) and many other features are available to the OEM choosing the SC400 reference design and Embedded BIOS.
Introducing the Élan SC400 Evaluation Board and its Embedded Features
The SC400 evaluation board (Figure 1) is a highly flexible embedded hardware design coupled with feature- rich, pre-boot firmware, Embedded BIOS, from General Software. Here we’ll visit different options for console I/O, mass storage, Flash programming, power manage- ment, and special software functions like Manufacturing Mode, the Debugger, and the Windows CE loader—
CE ReadyTM.
Console I/O:
Keyboard and Display Options
Handheld, mobile, embedded, and consumer electronics all have differing console requirements; some have no console in the traditional sense and others have remote consoles, or special keyboards and displays. The installed SC400 evaluation board BIOS includes support for console redirection, LCD display, ISA VGA, and VL local bus VGA.
Experimenting with Console I/O
To give the feeling for how the OEM can add policy to the BIOS adaptation, we’ve added a bit of code to the SC400EV’s Board Personality Module to determine which display is in use, and then redirect on that basis.
If you plug in an ISA VGA card into an ISA slot, then the BIOS detects this and uses the standard PC/AT keyboard and VGA display. If the ISA VGA card is unplugged, and the VL bus daughter card is installed on the board, then the BIOS uses the VL bus VGA display and the PC/AT keyboard.
If an LCD display is attached to the SC400EV board with the LCD daughter card, then the LCD and PC/AT keyboard are used.
Fig. 1. AMD SC400 Evaluation Board.
Finally, if no output device is attached, then the BIOS switches to a redirected console mode during POST, so that all console I/O is routed over the COM1 RS232 port at 9600 baud, no parity, and one stop bit—try this with your favorite terminal program. If you’re using HyperTerminal, make sure you select “no flow control”
in the session properties, and don’t forget that Hyper- Terminal doesn’t actually use these parameters until after you save, exit, and restart its session.
Console Redirection over Serial Links
For headless systems (those without keyboards and video monitors), Console Redirection is perhaps the most important feature of Embedded BIOS. While simple in principle, Console Redirection is actually a dynamic feature that interplays with other software features of Embedded BIOS.
There are really three types of console redirection in an embedded environment that uses a BIOS. First, using BIOS INT 10h and INT 16h services, the OEM can redirect POST messages and those printed by DOS and other applications.
Second, the BIOS debugger uses console I/O services to interact with the user. In some cases, it is desirable for this console to be the same one as the POST/DOS console, and in others (i.e., graphical environments), it is best to have the debugger output streamed over an RS232 connection to a Windows Terminal session.
Third, the Setup screen system uses console I/O services (including direct cursor addressing, which is translated transparently by the Embedded BIOS Console Redirec- tion facility). Some embedded designs use a secondary COM port for this, allowing field service engineers to access the Setup screens independently of the end user’s COM port connection to the device. This allows the system to be controlled at the lowest level.
These three channels of I/O are defined in the SC400EV project file. While the reference design project file sets the redirection for each channel to the standard keyboard and video display, the OEM choosing the SC400EV reference design can redirect those channels statically to any combination of COM ports.
Additionally, at run-time, the OEM’s Board Personality Module routines can redirect output of any component during POST or during post-boot steady-state, and even applications can call INT 15h at run-time to redirect the console to another device.
The Application Flash Array
Most handheld and mobile embedded products require mass storage without the expensive real estate consumed by a hard drive or floppy drive. The Élan SC400’s three 2MB x 16 Flash ROM parts total 12MB of mass storage, the perfect medium for the Resident Flash Disk feature of Embedded BIOS to use for emulating floppy and hard disk drives. (Later, we’ll see how to use this array for other purposes, such as CE Ready, the Windows CE bootloader.)
The configuration of the disk emulation feature at the BIOS level is a two-step process. First, the Flash types, geometry, and interleave are specified to the BIOS through the adaptation’s project file, so that the right Media Technology Drivers (MTDs) will be built into the BIOS, allowing read, write, and erase operations on the array. The second step is the configuration of the right File System Drivers (in this case, the Flash disk), specifying the location and size of the disk’s Flash memory supported by the MTDs.
Media Technology Driver Configuration
Flash arrays are organized in many different ways, and Embedded BIOS supports a wide range of geometries.
Each Flash memory component contains one or more erasable blocks of varying sizes, and may have an 8-bit, 16-bit, or 32-bit data path. Designs may gang-together multiple Flash components in parallel, to increase the effective data path width; this technique is called interleaving. It is common for 8-bit and 16-bit parts to be interleaved in 2-way or 4-way (two components wide or four components wide) configurations, and each of these combinations requires a different programming algorithm to engage in the same protocols with each component in the array, in parallel.
Embedded BIOS helps manage this complexity. Its Media Control Layer and Media Technology Drivers (MTDs) abstract the Flash programming algorithms and hide the underlying Flash array’s physical programming requirements from the RFD disk emulation software.
MTDs are available for all AMD Flash parts, as well as for ROM and RAM arrays.
; Starting Ending Technology
; Phys Addr Phys Addr Driver Name ; --- --- ---
MEDIA_REGION 000000000h, 01fffffffh, Ram ; system RAM.
MEDIA_REGION 020000000h, 03fffffffh, Amd8_2 ; Area mapped for Flash disk.
MEDIA_REGION 040000000h, 048ffffffh, Bulk8_1 ; ROMCS0#: up to 512KB bulk part.
MEDIA_REGION 048000000h, 04fffffffh, Amd8_1 ; ROMCS0#: up to 512KB bulk part.
MEDIA_REGION 050000000h, 05fffffffh, Amd8_2 ; ROMCS0#: 8bit 2way 29F016 pair.
MEDIA_REGION 080000000h, 0bfffffffh, Amd8_2 ; ROMCS1#: 8bit 2way 29F016 pair.
MEDIA_REGION 0c0000000h, 0ffffffffh, Amd8_2 ; ROMCS2#: 8bit 2way 29F016 pair.
In the case of the Élan SC400 reference design, the AMD 8-bit, two-way interleave drivers support the 16- bit wide AMD Flash components on the board. Figure 2 shows the MEDIA_REGION table for the Élan SC400 BIOS adaptation that defines the Flash drivers for the different chip selects. The region starting at media address 20000000h is actually a virtual address range that combines the three separate Flash components into one virtual Flash array.
Windowing Flash with the SC400’s MMUs
The Élan SC400’s application Flash parts are tied to the SC400’s CS0, CS1, and CS2 chip select lines, making them accessible through the programmable MMUs on the SC400 microprocessor. Embedded BIOS handles the programming of the MMUs automatically, and estab- lishes a 32-bit media address space that allows the OEM to specify where parts are located. The assigned range of addresses are as follows:
Media Address Range Actual Hardware 00000000h-1fffffffh ISA Bus and DRAM 20000000h-2fffffffh Virtual area
30000000h-3fffffffh PCMCIA slots 40000000h-7fffffffh ROMCS0 device 80000000h-bfffffffh ROMCS1 device c0000000h-ffffffffh ROMCS2 device As you can see from the above table and the example MEDIA_REGION table in Figure 2, it’s easy to assign BIOS functionality to parts tied to chip selects, or PCMCIA slots. ROM disks and RAM disks use the same mechanism; just different Media Addresses.
Emulating Disks in ROM, RAM, and Flash
Embedded in the core BIOS itself, are disk drivers for IDE, ATA, and floppy disks, as well as ROM, RAM, and Flash disks. The memory-oriented drivers emulate physical disk drives by receiving INT 13h (disk I/O) requests from operating system software when it reads and writes to what it believes are physical disk drives.
The ROM, RAM, and Flash disks present artificial geometry (heads, tracks, and sectors) to the operating system through this interface, just as the floppy disk
and hard disk drivers do. Internally, however, the drivers convert this artificial geometry into logical block addresses (LBAs) and use read, write, and erase opera- tions on the underlying media to record 512-byte user sector data and maintain a record of the locations of those data for later retrieval.
The configuration of the File System Drivers in the BIOS is based entirely on the simple directives in the Embedded BIOS Project File for the Élan SC400 (Figure 3.) In the listing, two floppy drives, two IDE hard drives, three soft-formatted Flash disks, and one
PCMCIA ATA hard drive are configured as file systems with the FILE_SYSTEM directive. Once configured in the build, the end user of the BIOS can selectively enable them in the Setup screen system.
Experimenting with the BIOS Flash Disk
The reference design is a great platform to experiment with Flash disks. Three sizes have been preconfigured in the BIOS build, so you’ll need to enter the SETUP screen to assign one of them to drive C:. Once you’ve done this in BASIC setup, select “Write to CMOS and Exit”, then reenter setup and select the “Format Flash Disk” menu item. This procedure low-level formats the Flash region. Then, after this is done, you can let the target boot from another drive, and FORMAT /S the C:
drive. Now the Flash disk is bootable and ready to use as a solid state disk.
You can also perform the high-level FORMAT /S procedure and copy files around remotely, using the BIOS’s Manufacturing Mode feature, described later.
Remember that when you change Flash disk sizes in the setup screen, you’ll need to redo the low-level formatting
; Note the address used for the RFD in the table below starting at
; 20000000h are translated in the SC400EVR board module to cause all
; the ROM_CS lines to be merged into a single media address range so
; the RFD can use all of the application Flash for one disk unit.
;
; Type Device Start addr Length SETUP name (unique)
; ---- --- --- --- ---
FILE_SYSTEM Soft, Floppy, 0h, 0h, "Floppy 0"
FILE_SYSTEM Soft, Floppy, 1h, 0h, "Floppy 1"
FILE_SYSTEM Hard, Flash, 020000000h, 000B80000h, "11.5MB Flash"
FILE_SYSTEM Hard, Flash, 020000000h, 000800000h, "8MB Flash"
FILE_SYSTEM Hard, Flash, 020000000h, 000400000h, "4MB Flash"
FILE_SYSTEM Hard, Ide, 0h, 0h, "Ide 0"
FILE_SYSTEM Hard, Ide, 1h, 0h, "Ide 1"
FILE_SYSTEM Hard, Ide, 2h, 0h, "PCMCIA ATA card"
Fig. 3. Configuration of File System Drivers in the Embedded BIOS Project File for Élan SC400.
process within the setup main menu, as the internal structure of the Flash disk needs to take into account the different Flash disk geometry.
You’ll also want to experiment with various other drives in the system. You can add a floppy drive as drive A:
and perhaps a bootable hard disk as drive C:. Then, your Flash disk can be assigned to D:. Note that not all versions of DOS, including MS-DOS, can SYS to drive D: and then boot from that drive after it has moved in the setup screen to be the first drive. If you want to make C: bootable, you’ll need a floppy disk drive or Manufacturing Mode.
DOSes Available for Smaller Systems
Two DOSes come with the Embedded BIOS Adaptation Kit from General Software—it’s own micro-sized Embedded DOS-ROMTM operating system (licensed free with the BIOS) and Lineo’s DR-DOS. Other industry- standard operating systems can also be used.
Using the Resident Flash Disk with Protected Mode Operating Systems
Once Embedded BIOS boots an operating system from the RFD, the operating system may continue to use INT 13h (disk I/O) BIOS services or might use only protected mode drivers. When the latter is the case, General Software can provide a protected mode version of its RFD file system for virtually any environment, including Windows NT, VxWorks, and real-time environments such as PharLap’s Real Time Embedded Tool Suite.
Protected mode drivers from General Software and its partners are licensed separately from the Embedded BIOS firmware itself.
Launching Windows CE with CE Ready
Some operating systems, such as Windows CE, are loaded into RAM instead of executed in place. Embed- ded BIOS can launch XIP images, but it can also load images in various formats from either files on disks or their emulators, or from ROM/Flash memory images.
The Flash array in the Élan SC400 is ideal for storage of the Windows CE image (NK.BIN) that is produced by an adaptation of the Microsoft Embedded Tool Kit (ETK).
When the RFD is used to treat the Flash array as a disk drive, the NK.BIN file can be copied into the drive itself, and then loaded by the Embedded BIOS Windows CE Launcher. Alternatively, NK.BIN can be loaded from a specific Media Address (see the Flash section), without the use of the Flash disk.
This capability, called CE Ready, is actually just a specific use of a more general architecture built into Embedded BIOS—the integrated Load Image facility.
Using this system, the OEM can instruct Embedded BIOS to load into RAM a variety of images in specific formats from disks or memory regions, and optionally begin their execution. For a look at how this feature is configured in the project file, see Figure 4 below.
The Embedded BIOS Image Loader natively supports the Windows CE (NK.BIN) image format, as well as a raw format, that performs no translation. Additional methods can be added by the OEM for a particular application, without modifying the core software.
Experimenting with the Windows CE Loader
Try loading Windows CE on the Élan SC400 board.
You’ll need a generic version of NK.BIN (such as the version that LOADCEPC can run from the DOS prompt) copied onto the root directory of a hard drive or ATA drive.
Next, boot the target and enter the BASIC setup screen, select the drive to be the first bootable drive, and in the bottom of the left-hand “Drive Assignments” box, change “Boot Type” from “Boot Record” to “Windows CE”. This causes the BIOS bootstrap routine to look for bootable files in the drive’s root directory instead of loading the boot record on the drive. Finally, select
“Write to CMOS and Exit”, and boot the target. Win- dows CE boots, with VGA display, PS/2 mouse, and PC/AT keyboard.
OPTION_SUPPORT_WINCE = 1 ; enable WINCE jump entry.
OPTION_CMOS_LOAD_WINCE = 1 ; set default to load Windows CE.
LOAD_IMAGE "NK.BIN", WinCe, 000000000h, 000000000h
Fig 4 Configuration of Windows CE Launcher in the Embedded BIOS Project File. This example loads NK.BIN using the WinCe load method.
In-System Flash Update/Programming
The Élan SC400 reference design employs two types of Flash in the system—a bulk erase Flash and sectored Flash parts in the large Flash array. A common set of BIOS services provided by Embedded BIOS allow application programs, as well as the debugger and Manufacturing Mode, to read, write, and erase any or all of the Flash in the system.
There are many applications of Flash control. Starting with the OEM’s board bring-up process, Flash program- ming commands in the debugger verify the correctness of the OEM’s SC400-based design. The OEM can use debugger commands to interactively read and write Flash memory and erase whole blocks of Flash.
Manufacturing Mode utilizes the Flash programming commands so that it can update the files on any disk or their emulators (such as the RFD) or even the BIOS.
The REFLASH.EXE utility (part of a suite of programs that comes with the Embedded BIOS Adaptation Kit) uses the Flash programming interface supported by the BIOS to update copies of itself on the target. Unlike other Flash update programs, REFLASH.EXE uses the services of the BIOS to be installed on the target, not the services of the BIOS currently running. This means that the target’s BIOS ROM can be safely updated even if it is accidently programmed with an incorrectly-configured copy of the BIOS.
Experimenting With Flash in the Debugger
To use the debugger to display the contents of the Flash array, boot the target, enter the main setup screen, and select “BIOS Debugger.” From the debug prompt, use the RFL (Read Flash) command:
EB43DBG: RFL 2000:0000 (see Fig 2) ... Flash display is printed here ...
EB43DBG: HELP (displays commands) ... Other Flash commands displayed here ...
You can experiment with the other Flash commands, too. RFL reads from Flash, WFL writes to Flash, EFL erases Flash blocks, SFL sets a region of Flash to a fill value, and UFL updates Flash from another memory location, like a block copy. Be careful not to write to or erase Embedded BIOS at the top of the application
Manufacturing Mode Host Link
While the BIOS in a desktop PC only needs to boot an operating system, embedded systems and consumer electronic devices often need a special way for the device to be reprogrammed either in manufacturing or in the field. Embedded BIOS provides this capability with its unique Manufacturing Mode—a special boot mode that responds to requests from a remote host over a high- speed serial connection.
Manufacturing Mode can be started in several ways during BIOS POST on OEM designs based on the Élan SC400. First, the OEM can add a special board module routine to test certain hardware in the board’s design (i.e., an I/O port or UART MSR) to determine if a hardware signal is present that signals the target’s need to boot into Manufacturing Mode instead of booting the operating system. This routine returns its decision to POST, which starts Manufacturing Mode.
Manufacturing Mode can also be invoked on critical POST errors, if the OEM desires. This allows self- contained mobile or handheld devices, which have developed a systemic failure, to enter a mode whereby they can be remotely tested and reprogrammed in the field with a host.
Embedded BIOS’s POST can also invoke Manufacturing Mode as a standard boot activity, just as it can boot DOS in ROM, boot an operating system from any drive, or enter the ROM debugger.
The high-speed Manufacturing Mode link can operate up to 115kbaud over standard UARTs, including those that drive infrared (IrDA or TV Remote) transceivers.
On the host (a laptop or PC-compatible), General Software provides disk redirection software that (under DOS or Windows) allows the user to treat the target’s disks as additional drives. This means that a previously- unformatted target drive can be formatted and loaded with an operating system and application program files, all under batch file or program control on the host.
Null Modem Cable Élan SC400 board
running Embedded BIOS in Manufacturing Mode
Host Laptop or PC running DOS with MFGDRV.SYS
device driver and HOST.EXE
Additional host-side libraries are provided to expose the Manufacturing Mode protocol via Application Program- ming Interfaces (APIs) that can be called by any C/C++ program. A sample application, complete with full source code, shows how to re-Flash the Élan SC400 target, and test memory exhaustively.
Experimenting with Manufacturing Mode
To watch Manufacturing Mode work on your Élan SC400 board, you’ll need to set up the target and the host. On the Élan SC400, the easiest way to start Manufacturing Mode is to boot the target, go into the main setup menu, and select “Manufacturing Link.”
You’ll also need to set up your host with the Manufactur- ing Mode driver. A DOS-compatible driver called MFGDRV.SYS is available on General Software’s web site. Install this driver in the CONFIG.SYS file, boot the machine in MS-DOS mode, and finally connect a null modem cable from the host’s COM1 port to the Élan SC400’s COM1 port.
The next step is to use the HOST.EXE program (also from General Software’s web site) to ping the target to see if the software and cables are set up properly. From the DOS prompt on your DOS host machine, run HOST and select “PING TARGET” from the main menu. The target should respond after a ping or two.
If the PING works, you’re ready to exit the program and manipulate the target’s drives from the comfort of your host machine. (Remember to have the target’s drives actually enabled and set up properly from the Élan SC400’s setup screen.)
With all this set, you should have an additional drive beyond your last hard drive letter (probably, D:), that you can switch to and use DIR, COPY, and all the other DOS commands to manipulate.
Keep in mind that the link is set to 56KB to allow for some slower hosts, and this can be changed at BIOS build time. Also, to optimize performance, you may wish to disable disk caching on the redirected drive by using a command like “SMARTDRV D-”.
Fig. 5 Manufacturing Mode connects host PCs with embedded SC400 targets running Embedded BIOS in a pre-boot environment.
Experimenting with the BIOS Debugger
Embedded BIOS is the only BIOS to have a fully capable debugger. Features include—
• disassembler
• breakpoints
• 32-bit register and memory access
• chipset, Super I/O, PCI, and Flash programming commands
• A20 and cache controls
In addition, you’ll find many other BIOS-level functions, like performing disk I/O to/from RAM.
These facilities are all available in a command-line interface that is completely integrated into the core BIOS. This integration means facilities can be invoked any time and used to debug the hardware during board bring-up and the BIOS adaptation.
Entering the debugger can be accomplished in a number of ways. The easiest is to go into the setup screen’s main menu during POST, and select “Enter BIOS Debugger.”
Another way to enter the debugger is to simultaneously press the CTL and LEFT SHIFT keys. In the BASIC setup screen, the debugger can even be selected as a boot-time activity, in case other boot options fail.
Once in the debugger, a prompt (EB43DBG:) will appear, and you can type a command (or several, separated by semicolons.) Try HELP first, for a list of the commands available on the target. Then, refer to the debugger section of the Embedded BIOS Reference Manual.
To exit the debugger, use the “R” (go) command. If you used CTL+SHF to enter at a DOS prompt, remember that the prompt has already printed and DOS is waiting for your next command.
Here are some samples for using the debugger:
EB43DBG: D F000:0000
... display dump of BIOS at segment F000h ...
EB43DBG: V 13
... display the INT 13h interrupt vector ...
EB43DBG: U
... unassemble code at that location ...
EB43DBG: RFL 4000:0000
... display CS0 Flash device (see Fig 2 for addresses) ...
EB43DBG: CSR D3
... display the SC400’s D3h chipset register ...
EB43DBG: CSW D3 xx
... write xxh to the SC400’s D3h chipset register ...
We recommend experimenting with the CSR and CSW commands to see how the SC400’s registers can be
Advanced Power Management
Embedded BIOS’s integrated power manager provides industry-standard APM services to operating systems and applications, while allowing the OEM to completely determine what devices in the system will participate in power management and what policies will be used for those devices.
Callouts from the core BIOS to the OEM’s board-level personality module allow for customization of all states and state transitions. For details on how this mechanism work (beyond the scope of this 8-page white paper), print the power management section of the Embedded BIOS Reference Manual.
Some Closing Remarks
The Élan SC400 platform is a great choice for proto- typing embedded applications that need solid state storage, power management, remote access, and special console I/O features. Those applications can all benefit from the Embedded BIOS pre-boot firmware that has been tailored to the Élan SC400 platform.
AMD’s Partnership with General Software
AMD and General Software worked closely together to bring the new Élan SC400 evaluation board to market.
“AMD’s selection of General Software was a logical choice,” says Richard Russell, AMD’s System Software Engineering Manager, Embedded Processor Division.
“General Software’s technical capabilities, product maturity, market vision, and outstand- ing support offered to our embedded custom- ers is something that we want every AMD customer to experience when starting a new embedded design.”
In addition to the Élan SC400 reference design, General Software supplies the BIOS firmware for other AMD designs, such as those based on the AMD SC300 Elan and Am186 embedded processor family, and the Am486PCI Customer Development Platform.
For more information and news about AMD’s SC400 and other AMD products supported by General Software, visit the General Software web site at www.gensw.com or AMD’s site at www.amd.com.
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