W83L518D

Publication Release Date: May 11, 2005

- 11 -

Revision 1.0

6.2.3

Extended Function Index Register (EFIR), Extended Function Data Register (EFDR)

After entering Extended Function mode, Extended Function Index Register (EFIR) must be written

with an index value (02h, 07h-FEh) to specify which configuration register is to be accessed through

Extended Function Data Register (EFDR). EFIR is a write-only register at I/O address 2Eh or 4Eh (as

described in section 6.2.1) on a PC/AT system and EFDR is a read/write register at I/O address 2Fh

or 4Fh.

6.3

Configuration Sequence

To program configuration registers, specific configuration sequence must be followed:

(1) Write 83h to EFER twice to enter Extended Function mode.

(2) Select logical device select register by writing 07h to EFIR.

(3) Select logical device by writing a value to EFDR.

(4) Select control/configuration register by writing its index to EFIR.

(5) Access selected control/configuration register through EFDR.

(6) Repeat step 4 ~ 5 as needed.

(7) Leave Extended Function mode by writing AAh to EFER.

Step 2 and step 3 are not necessary for accessing global register (index 00h to 2Fh).

6.3.1

Software programming example

The following example is written in Intel 8086 assembly language. EFER and EFIR are assumed to

be at 2Eh, and EFDR is at 2Fh. Use 4Eh/4Fh instead of 2Eh/2Fh if HEFRAS (bit 6 of CR26) is set.

;-----------------------------------------------------------------------------------

; Enter Extended Function mode, interruptible double-write

|

;-----------------------------------------------------------------------------------

MOV

DX, 2Eh

MOV

AL, 83h

OUT

DX, AL

OUT

DX, AL

;-----------------------------------------------------------------------------

; Configure logical device 1, configuration register CRF0 |

;-----------------------------------------------------------------------------

MOV

DX, 2Eh

MOV

AL, 07h

OUT

DX, AL

; point to Logical Device Number Reg.

MOV

DX, 2Fh

MOV

AL, 01h

OUT

DX, AL

; select logical device 1