PicoWeb Pcode Definitions

PicoWeb Pcode Instruction Definitions (v1.34)

All pcode instructions take one of the following forms:

opcode
opcode	p1
opcode	p1,p2
opcode	p1,p2,p3

where:

opcode	pcode opcode listed in one of the PicoWeb pcode instruction tables
p1-p3	pcode operand (p1, p2, p3) shown in the PicoWeb pcode instruction tables

All pcode operands (p1, p2, p3) may be expressed in one of seven different forms, one normal form, three different indirect forms, and three different string literal forms, as follows:

p	effective operand is 16-bit value p (normal form)
[p]	effective operand is 16-bit word stored beginning at SRAM address p
[byte p]	effective operand is 8-bit byte stored at SRAM address p
[swap p]	effective operand is 16-bit word at SRAM address p with high/low bytes swapped
"..."	effective operand is address of character string ("...") in the current code segment (.cseg or .eseg)
cseg "..."	effective operand is address of character string ("...") in program memory (.cseg)
eseg "..."	effective operand is address of character string ("...") in external SEEPROM memory (.eseg)

Warning: If any of the indirect operand forms are used in a given pcode instruction instance, then the size of any (and all) immediate (i.e., imm operands) operands used in that pcode instruction instance is reduced from 16 bits to 14 bits.

Notes regarding the PicoWeb pcode tables which follow:

a indicates an SRAM address

* a indicates the 16-bit word starting at SRAM byte address a

a[n] indicates the contents of the SRAM byte at address (a + n)

imm is an immediate 16-bit word value

ppc signifies the pcode program counter

s signifies the start address of a zero-terminated string in on-chip flash memory or external SEEPROM memory
addr signifies the address of a pcode opcode (in on-chip flash or external SEEPROM memory)
The pcode flags (Z, C, N) are separate from the AVR processor flags
Z is the pcode zero flag
C is the pcode carry flag
N is the pcode negative flag (i.e., sign bit)

low(x) indicates the low 8 bits of a 16-bit word value x

swap(a) indicates an exchange of the low and high bytes of a 16-bit word a

PicoWeb Pcode General Purpose Instructions

Opcode	p1	p2	p3	Description	Operation	Flags
paddwi	a	imm		Add immediate to word	* a = * a + imm	Z,C,N
pandwi	a	imm		Logical AND word immediate	* a = * a & imm	Z,N
pbegin				Begin executing pcode	rcall pcode
pbitwi	a	imm		Bit test word immediate.	* a & imm	Z
pcall	addr			Call pcode routine	push ppc onto pcode return stack; ppc = addr
pclrw	a			Clear word	* a = 0
pcmpbi	a	imm		Compare byte immediate	a[0] - low(imm)	Z,C,N
pcmpn	a	b	n	Compare two buffers in SRAM	for (i=0; i<n; ++i) a[i] - b[i];	Z
pcmpwi	a	b		Compare word immediate.	* a - imm	Z,C,N
pcomw	a			Ones complement word.	* a = 0xFFFF - * a	Z,C,N
pdecw	a			Decrement word	* a = * a - 1	Z,C,N
pdiv	a	b	c	Unsigned 16-bit divide, 32-bit result	* a = * b / * c; * (a+2) = * b % * c;
pend				Stop executing pcode	.dw 0
pincw	a			Increment word	* a = * a + 1	Z,C,N
pjump	addr			Unconditional jump within pcode	ppc = addr
pjumpeq	addr			Jump within pcode if equal	if (Z == 1) ppc = addr
pjumplo	addr			Jump within pcode if lower	if (N == 1) ppc = addr
pjumpne	addr			Jump within pcode if not equal	if (Z == 0) ppc = addr
pmemcpy	a	b	n	SRAM memory copy	for (i=0; i<n; ++i) a[i] = b[i];
pmovb	a	b		Move byte	a[0] = b[0]
pmovbi	a	imm		Move byte immediate	a[0] = low(imm)
pmovwi	a	imm		Move word immediate	*a = imm
pmul	a	b	c	Unsigned 16-bit multiply, 32-bit result	a = (b ´ c) & 0xFFFF; (a+2) = (b ´ c) >> 16
pnegw	a			Two’s complement word	* a = 0 - * a	Z,C,N
pret				Return from pcode routine	ppc = pop pcode return stack
pshnw	a	n		Logical shift 16-bit word n bits	if (n > 0) * a = (* a << low(n)) else * a = (* a >> low(n));
psubwi	a	imm		Subtract word immediate	* a = * a - imm	Z,C,N
pwdr				Watchdog timer reset	wdr
pxorwi	a	imm		Exclusive OR word immediate	* a = * a ^ imm, set flags with low(* a)	Z,N

Notes:

A pcode transfer of control instruction (e.g., pcall, pjump, etc.) must have as its target address another pcode instruction. Transfering control from pcode directly to AVR assembly language will produce unpredictable results!
Pcode must be entered from AVR assembly language using a pbegin instruction. Return to AVR assembly language must be done using a pend instruction. Unpredictable results can be expected if these rules are not followed!

PicoWeb Pcode Input/Output Instructions

Opcode	p1	p2	p3	Description	Operation	Flags
pcrlf				Print CR,LF	printf("\r\n")
phexbi	a			Print hex byte immediate	printf("%02x", (a & 0xFF))
pprint	s			Print string	printf("%s", s)
pprintb	s	a	n	Print bytes in hex with string	if (s != 0) printf("%s", s); for (i=0; i<n; ++i) printf("%02x", a[i]);
pprintv	s	imm		Print string with 16-bit hex value	if (s != 0) printf("%s", s) else putchar(‘ ‘); printf("%04x", imm);
pputc	imm			Print character immediate	putchar(imm & 0xFF);
pputcb	a			Print character	putchar(a[0] & 0xFF);
pser_getc	a			Check/get serial port character	if (character ready) a = getchar(), Z = 0 else Z = 1;	Z
pser_mode	bin			Flush and set serial port mode	Flush any buffered characters, then if (bin = 0) set normal mode; else set pass-all (binary) mode
pser_putc	imm			Write immediate byte to serial port	Wait for a "transmit done" indication on serial port, then write low(imm) to UART
pspace				Print a space	putchar(‘ ‘)

Notes:

The operation putchar(ch) behaves as follows: If (putc_b == 0), the byte ch is written to serial port,. If (putc_b ¹ 0), the byte ch is sent to transmit stream or stored in holding buffer pending flush of transmit buffer.
The operation printf() behaves identically as the previously described putchar() operation

PicoWeb Pcode Network Instructions

Opcode	p1	p2	p3	Description	Operation	Flags
paddn	a	b	n	Add n-byte integers (network byte ordering)	CF = 0; for (i=low(n)/2-1; i¹ 0; i-=1) * (a+2i) = swap(swap( (a+2i)) + swap( (b+2*i)) + CF);
pf2x	off	func	n	Output bytes to Ethernet transmit buffer starting at byte off with checksum	for (i=0; i<n; ++i) Xmit[off + i] = func(); where func returns 16-bit word in X register. A 16-bit network checksum accumulated into "chkacc".
pi2x	off	imm		Output immediate 16-bit word to Ethernet transmit buffer at byte off	Xmit[off] = imm
pprinta	s	eadd	n	Print bytes from Ethernet receive buffer with label	if (s != 0) printf("%s=", s); for (i=0; i<n; ++i) putchar(Recv[eadd + i]);
pprintr	s	off	n	Print words in hex from current receive buffer with label	if (s != 0) printf("%s=", s); for (i=0; i<2*n; ++i) printf("%02x", Recv[off + i]);
pprintt	s	off	n	Print words in hex from current transmit buffer with label	if (s != 0) printf("%s=", s); for (i=0; i<2*n; ++i) printf("%02x", Xmit[off + i]);
pr2s	a	off	n	Move bytes from current Ethernet receive buffer to memory	for (i=0; i<n; ++i) a[i] = Recv[off + i];
pr2x	off1	off2	n	Move bytes from current Ethernet receive buffer to Ethernet transmit buffer.	for (i=0; i<n; ++i) Xmit[off1 + i] = Recv[off2 + i];
ps2x	off	a	n	Move bytes from memory to Ethernet transmit buffer	for (i=0; i<n; ++i) Xmit[off + i] = a[i];
px2s	a	off	n	Move bytes from Ethernet transmit buffer to memory	for (i=0; i<n; ++i) a[i] = Xmit[off + i];
pz2x	off	n		Write zero bytes to transmit buffer	for (i=0; i<n; ++i) Xmit[off + i] = 0;

Notes:

Xmit[0] is the first byte of the Ethernet transmit buffer and Recv[0] is the first byte of the Ethernet receive buffer. Both point to the first byte of the Ethernet MAC address in the respective buffer (i.e., any NIC-specific header bytes are skipped).
The operation printf() behaves identically as the previously described putchar() operation

10/23/99 11:28 AM