W83787IF Datasheet, PDF (65/123 Pages) Winbond – WINBOND I/O WITH SERIAL-INFRARED SUPPORT

W83787IF
ABCHG (Bit 7):
This bit enables the FDC AB Change Mode. (The default value depends on DBENL /ABCHG at
power-on setting. If there is no setting, the default is normal mode.)
0
Drives A and B assigned as usual
1
Drive A and drive B assignments exchanged
Examples (debug instructions):
Example 7.4: Enable COM1 (3F8), COM2 (2F8), LPT1 (3BC); drives A and B assigned as in normal
operation.
Ex. 7.4
- O 250 89
- O 251 01
- O 252 0C
- O 250 00
Example 7.5: Enable only COM3 (3E8), LPT2 (278); assignments of drives A and B exchanged.
Ex. 7.5
- O 250 89
- O 251 01
- O 252 DB
- O 250 00
7.2.3 Configuration Register 2 (CR2) EFER = 89, EFIR = 2H
When EFER = 89H and EFIR = 02H, the CR2 register can be accessed through EFDR. The bit
definitions are as follows:
7 6543 21 0
CEA
EA3
EA4
EA5
EA6
EA7
EA8
EA9
Notes:
When the W83787IF is programmed into extension adapter mode, the contents of this register are a
base address for the extension adapter. When base addresses EA3-EA9 are written into CR2, both
the XRD and XWR pins will be active low simultaneously and an adapter connected to the parallel
port can latch the same base address through pins XD1-XD7. After the base address is latched into
CR2, a subsequent read/write cycle to this same base address will generate an XRD or XWR signal.
If CEA is set to 0, then the W83787IF will compare system addresses SA9-SA3 with EA9-EA3 to
generate a compare-equal signal for this read/write command to access the Extension adapter. If
CEA is set to 1, then only EA9-EA4 are used in this comparison.
- 65 -
Publication ReleaseDate:Sep 1995
Revision A1