45181 Parallax Inc, 45181 Datasheet - Page 163

• Manufacturer Part Number: 45181
• Description: SX TECH TOOL KIT NO POWER
• Manufacturer: Parallax Inc
• Series: SXr
• Type: Microcontrollerr

Specifications of 45181

• Contents: SX Book, SX Key, SX Tech Board, Samples, Resonators, Cable and Manual
• Product: Microcontroller Basic Stamps
• Operating Supply Voltage: 5 V
• For Use With/related Products: SX MCUs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

15.2.14 Jumping Across Pages
When a JMP instruction is executed and the intended destination is on a different page, you must set
the page select bits to point to the desired page before the jump occurs. This can be done discretely with
SETB and CLRB instructions or by writing a value to the STATUS register. The SX offers a single-cycle
instruction called PAGE that sets the page select bits for you. See “Dealing with Code Pages” in Chapter
10.6 for more information. NOTE: Using the @ symbol in the JMP instruction (JMP @label) will cause the
assembler to insert the PAGE instruction before your JMP, during assembly.
15.2.15 The Call Instruction
When a CALL instruction is executed, four things occur:
1) the current value of the program counter is incremented and pushed onto the top of the stack;
2) the lower eight bits of the address of the label are copied into the lower eight bits of the
3) the ninth bit of the PC is cleared to zero
4) the page select bits of the STATUS register are copied into the upper bits of the PC. Since bit 8 is
program counter
cleared, the call destination must start in the lower half of any page of code space. i.e. $00-$FF,
$200-$2FF, $400-$4FF, etc.
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Figure 31 - Jumping Across Pages
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PAGE label
SX-Key/Blitz Development System Manual 2.0 Parallax, Inc. Page 163
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15 Appendix E: SX Data Sheet
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JMP label
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