Web 51 P-Code Interpreter

Part 3 - P-Instructions for basic network operations

Contents of LIBK, basic network functions

*instruction*	*parameters*	*description*	*operation*	*flags*
ptstr2s	(B)a, (W)offset, (W)lng	Compare String to Receive Frame	for(i=0;i<lng;i++)(B)@a[i]-(B)@receive[offset+i])	zflag
ptstr2e	(B)e, (W)offset, (W)lng	Compare eepromString to Receive Frame	for(i=0;i<lng;i++)(B)@e[i]-(B)@receive[offset+i])	zflag
pr2s	(B)a, (W)offset, (W)lng	Copy from Receive Frame to String	for(i=0;i<lng;i++)(B)@a[i]=(B)@receive[offset+i])
px2s	(B)a, (W)offset, (W)lng	Copy from Xmit Frame to String	for(i=0;i<lng;i++)(B)@a[i]=(B)@receive[offset+i])
pi2x	(W)offset, (W)imm	Mov Word Immediate to Xmit Frame	(W)@xmit[offset]=(W)imm
ps2x	(W)offset, (B)a, (W)lng	Mov String to Xmit Frame	for(i=0;i<lng;i++)(B)@xmit[offset+i]=(B)@a[i])
pe2x	(W)offset, (B)e, (W)lng	Mov eepromString to Xmit Frame	for(i=0;i<lng;i++)(B)@xmit[offset+i]=(B)@e[i])
pc2x	(W)offset, (B)c, (W)lng	Mov codeString to Xmit Frame	for(i=0;i<lng;i++)(B)@xmit[offset+i]=(B)@c[i])
pz2x	(W)offset, (W)lng	Mov Zero to Xmit Frame	for(i=0;i<lng;i++)(B)@xmit[offset+i]=0)
pr2x	(W)xmit_offset, (W)receive_offset, (W)lng	Mov Receive Frame to Xmit Frame	for(i=0;i<lng;i++)(B)@xmit[xmit_offset+i]=@receive[receive_offset+i])

(B) or (BYTE) - 8-bit argument or operation
(W) or (WORD) - 16-bit argument or operation
a, b - address of data in processor memory (DATA/IDATA)
c - address of data in processor PROGRAM memory (CODE)
e - address of data in processor EEPROM (eXDATA)
@a - data in processor memory at address a
@a[i] - data in processor memory at address a + i
@a[offset + i] - data in processor memory at address a + offset + i
@c[i] - data in processor PROGRAM memory at address c + i
@e[offset + i] - data in processor EEPROM at address e + offset + i
imm - immediate constant
lng - string length

Most P-Instructions use DMA channel of the Ethernet controller to directly transfer data between the data field and the controller. Exceptions exist: the pi2x instruction uses variable workreg to store the constant passed as its parameter; and the pr2x instruction must use transfer through a temp data area, since there are no separate DMA channels for transmitted and received frames. It copies data portion by portion using buffer ebuf.

*instruction*	*parameters*	*description*	*operation*	*flags*
xmit_frame	(W)lng	Transmit Xmit Frame	Transmit lng bytes to Ethernet
psendchar	(B)char	Write char to Xmit Frame	@xmit[tcpWritePointer++]=char
bflush		Flush ebuf to Xmit Frame

Similarly to pr2x, instruction psendchar does not write data directly into the Ethernet controller but uses buffer ebuf. Buffer is controlled by two global variables: tcpWritePointer contains offset in the xmit frame where data will be stored, and is automatically incremented as the data are copied from ebuf to the xmit frame. unwrited contains offset in ebuf; however, the actual offset is tcpWritePointer + unwrited. Before the first call to psendchar, both variables must be initialized - correct offset stored into tcpWritePointer and unwrited set to 0. It is necessary to call bflush after writing data with psendchar.

*instruction*	*parameters*	*description*	*operation*	*flags*
in_checksum		Calculate Frame checksum

in_checksum calculates checksum of the block stored in the Ethernet controller memory. The block is defined by its absolute address in the controller memory which is passed in the global variable chkaddr, and its length passed in global variable chklen. Result as well as initial value are passed in global variable chkaddr.