Format of Brooktree Bt8230 ATM controller configuration:
Offset	Size	Description	)
 00h 64 BYTEs	header (see #00878)
		(vendor ID 109Eh, device ID 8230h)
 10h	DWORD	address at which to map external memory (multiple of 16M)
		internal registers are mapped at offsets 0000h-01FFh; Bt8222
		  registers are mapped at 0200h-03FFh, and T1/E1 Framer
		  registers are mapped at 0800h-0FFFh.	Only 32-bit memory
		  accesses are used
 40h	BYTE	maximum burst length (00h not allowed, default = 10h)
 41h	BYTE	"SPECIAL_STATUS"
		bit 3: attempted to perform DMA on PCI while bus-mastering
			  disabled in PCI command word
		bit 2: PCI/DMA synchronization error occurred
		bit 1: PCI bus master encountered fatal error
		bit 0: direction of transaction which encountered error
			=0 write (refer to offset 48h)
			=1 read (refer to offset 44h)
		Note:	bits 3-1 are write-clear, bit 0 is read-only
 42h  2 BYTEs	unused
 44h	DWORD	current read target address for PCI bus master (read-only)
 48h	DWORD	current write target address for PCI bus master (read-only)
 4Ch 180 BYTEs	reserved
SeeAlso: #00790