Format of Econet command block:
Offset	Size	Description	)
 00h	BYTE	command code (see #03039)
---command 00h---
 01h	BYTE	direction (00h = read initialization data, 01h = set init data)
 02h	WORD	"TxCB" transmit control block size
 04h	WORD	"RxCB" receive control block size
		Notes:	TxCB and RxCB are always the same size in v1.05,
			  permitting any CB to be used for either receive
			  or transmit
			this command should not be used by applications to
			  set the buffer sizes
 06h  6 BYTEs	padding (0)
---command 01h---
 01h	BYTE	port number (00h = receive on all ports)
		if the RxCB is opened for RPC, the port number indicates the
		  allowable RPC (see #03040)
 02h	WORD	station number (FEFFh = broadcast)
 04h	BYTE	RPC flags
		bit 7: CB is open for RPCs only
		bit 6: restrict to RPC number given in next field
 05h	WORD	RPC number
 07h	BYTE	timeout in 1/2-second units (00h = never)
		if a timeout occurs, the RxCB can still receive data, and may
		  generate another event after the timeout unless it is
		  explicitly killed
 08h  4 BYTEs	padding (0)
---command 02h---
 01h	BYTE	control byte
 02h	BYTE	port number
 03h	WORD	station number
 05h	BYTE	number of retries
 06h	WORD	length of data to be sent (bits 14-0), 0000h allowed
		if bit 15 is set, no data will be transferred, but this field
		  will be updated (needed for peeking)
 08h	DWORD	-> destination address on remote machine
---command 03h---
 01h	BYTE	Control Block Handle
		FEh first filled-in RxCB
		FFh first TxCB which has been sent
 02h 10 BYTEs	padding (0)
---command 04h---
 01h	BYTE	Control Block Handle
 02h	BYTE	kill condition
		00h always
		01h kill only if bit7 of control byte is clear
		81h kill only if bit7 of control byte is set
 03h  9 BYTEs	padding (0)
		Notes:	control blocks are not freed until explicitly killed
			because all TxCBs for a given destination are stored
			  on a separate subchain, it is necessary to kill all
			  failed TxCBs to a given destination before any new
			  ones are opened to that destination
---command 06h---
 01h	BYTE	Control Block Handle
 02h	WORD	starting byte within CB to read
 04h	WORD	number of bytes
		if 0000h or greater than remaining bytes in CB, return all
		  bytes from starting byte to end of CB
 06h  6 BYTEs	padding (0)
---command 07h---
 01h	BYTE	subfunction
		00h-0Fh get/set M/C type (bit N=1 indicates to set byte N)
			four data bytes
		10h get station number
		11h set station number
		12h get Tx pause in 5ms units (default 20)
		13h set Tx pause
		14h get software version numbers
		16h get event enable mask
		17h set event enable mask
		18h get number of non-volatile bytes available
		80h+2N get non-volatile byte N
		81h+2N set non-volatile byte N
 02h	var	new data
Note:	all command blocks should be padded to twelve bytes with zeros if
	  needed
SeeAlso: #03036