TCALL (SPC700): Difference between revisions

Revision as of 05:23, 8 July 2024


Basic Info
Addressing Mode	Opcode	Length	Speed	Vector Address
Implied (type 3)	01	1 byte	8 cycles	$FFDE
Implied (type 3)	11	1 byte	8 cycles	$FFDC
Implied (type 3)	21	1 byte	8 cycles	$FFDA
Implied (type 3)	31	1 byte	8 cycles	$FFD8
Implied (type 3)	41	1 byte	8 cycles	$FFD6
Implied (type 3)	51	1 byte	8 cycles	$FFD4
Implied (type 3)	61	1 byte	8 cycles	$FFD2
Implied (type 3)	71	1 byte	8 cycles	$FFD0
Implied (type 3)	81	1 byte	8 cycles	$FFCE
Implied (type 3)	91	1 byte	8 cycles	$FFCC
Implied (type 3)	A1	1 byte	8 cycles	$FFCA
Implied (type 3)	B1	1 byte	8 cycles	$FFC8
Implied (type 3)	C1	1 byte	8 cycles	$FFC6
Implied (type 3)	D1	1 byte	8 cycles	$FFC4
Implied (type 3)	E1	1 byte	8 cycles	$FFC2
Implied (type 3)	F1	1 byte	8 cycles	$FFC0


Flags Affected
N	V	P	B	H	I	Z	C
.	.	.	.	.	.	.	.

TCALL (Table CALl) is an SPC700 instruction that calls a subroutine whose address is stored in the uppermost page. The low byte of the address of the vector (pointer to subroutine) is a function of the high nybble of the opcode, equal to $DE - n*2. The high byte of the vector address is always $FF.

No flags are affected.

Syntax

TCALL n

where n is the vector call number, a decimal integer from 0 to 15, which becomes the high nybble of the opcode.

External Links

Official Nintendo documentation on TCALL: Table C-16 Appendix C-9
anomie's SPC700 doc
https://forums.nesdev.org/viewtopic.php?t=13313

@@ Line 6: / Line 6: @@
 |'''Length'''
 |'''Speed'''
-|'''Target Address'''
+|'''Vector Address'''
 |+
 |[[Implied]] (type 3)
@@ Line 127: / Line 127: @@
 |}
-'''TCALL''' (Table CALl) is an [[SPC700]] instruction that calls a subroutine in the [[uppermost page]].  The low byte of the effective address which is called is a function of the high nibble of the opcode, equal to $DE - nibble*2.  The high byte of the effective address is always $FF.
+'''TCALL''' (Table CALl) is an [[SPC700]] instruction that calls a subroutine whose address is stored in the [[uppermost page]].  The low byte of the address of the vector (pointer to subroutine) is a function of the high nybble of the opcode, equal to $DE - n*2.  The high byte of the vector address is always $FF.
 No flags are affected.
@@ Line 137: / Line 137: @@
 </pre>
-where n is the vector call number, a decimal integer from 0 to 15, which becomes the high nibble of the opcode.
+where n is the vector call number, a decimal integer from 0 to 15, which becomes the high nybble of the opcode.
 === See Also ===