DM-COP8/20D National Semiconductor, DM-COP8/20D Datasheet - Page 147

• Manufacturer Part Number: DM-COP8/20D
• Description: CABLE FOR DEBUG MODULE 20-DIP
• Manufacturer: National Semiconductor

Specifications of DM-COP8/20D

• Accessory Type: 20-DIP Target Cable
• For Use With/related Products: MetaLink Debug Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *DM-COP8/20D

Syntax:
Description:
Operation:
VIS
Instruction
VIS
The purpose of the VIS instruction is to vector to the interrupt service
routine for the interrupt with the highest priority and arbitration rank-
ing that is currently enabled and requesting. The VIS instruction expe-
dites this procedure of vectoring to the interrupt service routine.
All interrupts branch to program memory location 00FF Hex once an in-
terrupt is acknowledged. Thus, any desired context switching (such as
storing away the contents of the accumulator or B or X pointer) is nor-
mally programmed starting at location 00FF Hex, followed by the VIS
instruction. The VIS instruction can be programmed at memory location
00FF Hex if no context switching is desired.
The VIS instruction first jumps to a double-byte vector in a 32-byte in-
terrupt vector program memory table that is located at the top of a pro-
gram memory block from address xyE0 to xyFF Hex. Note that xy is the
block number (usually 01) where the VIS instruction is located (each
block of program memory contains 256 bytes). This double-byte vector is
transferred to PC (high-order byte first), and then the program jumps to
the associated interrupt service routine indicated by the vector. These
interrupt service routines can be anywhere in the 32-Kbyte program
memory space.
Should the VIS instruction be programmed at the top location of a mem-
ory block (such as address 00FF Hex), the associated 32-byte vector table
is resident at the top of the next higher block (locations 01E0 to 01FF
Hex with the VIS instruction at 00FF Hex).
PCL <- VA (Interrupt Arbitration Vector generated by hardware)
PCU <- Program Memory (PCU,VA)
PCL <- Program Memory (PCU,VA+1)
Implicit
Addressing Mode
Instruction
Cycles
COP8SAx7 MICROCONTROLLER
5
Bytes Hex Op Code
1
B4
2-109