XT-CF-lite rev.1

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Lo-tech XT-CF-lite Board, Assembled

Note: This adapter has been superseded by the XT-CF-lite rev.2

The lo-tech XT-CF-lite rev.1 board is an 8-bit ISA CompactFlash adapter, providing bootable solid-state storage for any IBM compatible PC, including the original IBM Personal Computer 5150. The board has been designed to provide basic functionality in the same footprint as the XT-CFv3, but with SOIC 74xx series logic, thereby eliminating the need to program a CPLD and so simplifying construction.

As with the other lo-tech XT-CF Boards, the CompactFlash card is accessible through a custom-made ISA expansion slot bracket, such that the media can be exchanged without the need to open the PC case.

The board is powered by the XT-IDE Universal BIOS, provided through an in-system re-programmable 32KB (addressible) flash-based ROM. Since the BIOS is only 8KB, 24KB is available for other purposes, and is byte-programmable. The board can therefore function as a universal ROM board, regardless of whether the CompactFlash logic is used (or indeed populated on the PCB).

Specifications

  • 8-bit ISA card with header for type-I or type-II CompactFlash media
  • CompactFlash header configured to operate media in true-IDE mode
  • 5V supply to CompactFlash header can drive micro-drives or CompactFlash cards without any external power connection
  • Line driver for on-card and external activity LEDs (30mA power budget for external LED)
  • Low-cost flash memory chip for boot ROM, with 32KB usable
  • Port-mapped IO; supports both 8- and 16-bit instructions (via partial address decoding)
  • Utilises XT-IDE Universal BIOS (adapter type: 'XT-CF')

Design

Use of this design is provided subject to the lo-tech.co.uk Terms and Conditions.

Bill of Materials

Part Value Device Package Qty Farnell Mouser
C1 47uF CPOL-EUE2-5 E2-5 1 8767114 140-REA470M1ABK0511P
C2..7 0.1uF C-EUC0603 C0603 6 1414610 81-GRM18R71C104MA01D
CF1 N7E50-Q516 N7E50-Q516xx-50 N7E50-Q516xx-50 1 1267444 517-N7E50-Q516B-50-W
EXT.LED HD_LED PINHD-1X02_2.54-S 1X02-S 1 3418285 571-826629-2
IC1 - SST39SF0x0A DIP32 1 1896595 804-39SF010A7CPHE
IC2..3 - 74HCT688DW SO20W 2 1085321 771-74HCT688D-T
IC4 - 74HCT32D SO14 1 1201305 595-SN74HCT32D
IC5 - 74HCT04D SO14 1 1085299 771-74HCT04DAUJ
IC6 - 74LVC1G14 SOT-25 1 1893833 771-74LVC1G14GW-G
LED LEDCHIPLED_0805 CHIPLED_0805 1 1685055 630-HSMR-CL25
R1 0R R-EU_0207/10 0207/10 1 1700196 299-0-RC
R2 DNP - - - - -
R3, R5 1k R-EU_R0603 R0603 2 2008355 667-ERA-3AED102V
R4 160R R-EU_R0603 R0603 1 2059585 71-CRCW0603-270-E3
R6 5.6k R-EU_R0603 R0603 1 1739171 667-ERA-3AED562V
RN1 10K RN08 RN-9 1 9356819 652-4609X-1LF-10K
SW1 SW_DIP-8 EDG-08 1 9471596 774-2068ST
Socket DIL32 1 1654375 571-1-390263-2
  • Board design permits the use of a range of DIP-32 flash chips or 1, 2 or 4Mb:
  • Regardless of the chip used, the first 32KB only will be mapped into the PC address space
  • Base address configuration per DIP Switch Settings

Logic

The board logic provides two distinct functions:

  • Address decoding for the SST39SF0x0 flash chip
    • Address bus is matched to DIP switch settings via IC2, to generate ROM chip-enable
  • Address decoding for the CompactFlash header /CS0 and /CS1, via IC3, IC4 and IC5
    • Address bus is matched to DIP switch settings via IC3
    • CompactFlash header /CS0 and /CS1 are generated using logic similar to the Vintage-Computer XT-IDE Board, providing Base+10h for the alternate status register access
    • CompactFlash header /DA[0..2] are mapped to ISA A[1..3], thereby enabling 16-bit instructions, since A0 is not decoded

BIOS

ISA Bracket

Uses Lo-tech ISA Slot Bracket Type 1.

DIP Switch Settings

Switch Function On Off
1 ROM Enable Enabled Disabled
2 ROM Base Address A15 Low High
3 ROM Base Address A16 Low High
4 ROM Base Address A17 Low High
5 IO Port A5 Low High
6 IO Port A6 Low High
7 IO Port A7 Low High
8 IO Port A8 Low High

Default settings are ROM enabled, IO port 300h and ROM base address D000h:

1 2 3 4 5 6 7 8
ON ON OFF ON ON ON ON OFF

IO Range

IO Port Base Address Sw8 Sw7 Sw6 Sw5
200h ON ON ON ON
220h ON ON ON OFF
240h ON ON OFF ON
260h ON ON OFF OFF
280h ON OFF ON ON
2A0h ON OFF ON OFF
2C0h ON OFF OFF ON
2E0h ON OFF OFF OFF
300h* OFF ON ON ON
320h OFF ON ON OFF
340h OFF ON OFF ON
360h OFF ON OFF OFF
380h OFF OFF ON ON
3A0h OFF OFF ON OFF
3C0h OFF OFF OFF ON
3E0h OFF OFF OFF OFF

*Default

Note that the IO base address is set within the XTIDE Universal BIOS ROM image via the Universal BIOS Configuration and Flashing utility. The IO address set within that utility must match that configured on the card via the DIP switches. Should the IO port address be changed for any reason, the BIOS must be updated and re-flashed to the XT-CF-lite card (using the lo-tech XT-CF flash utility).

See Also