88 lines
2.7 KiB
Markdown
88 lines
2.7 KiB
Markdown
# Flags
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Locations shown below are relative to the start of flags, typically 0xFF00.
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Bits not defined read as zero and writing values will not have an effect.
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## Console | 0x0*
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### Status | CONSTS | 0x00
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| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
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| --------------- | --- | --- | --- | --- | --- | --- | --- | --- |
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| **Read/Write** | | | | | R | R/W | R/W | R |
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| **Default ** | | | | | X | 1 | 1 | X |
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| **Name** | | | | | ReadAvailable | ReadBlock | Enabled | Available |
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### Cursor X | CONPOSX | 0x01
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* 8-bit unsigned number
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* Read/Write
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### Cursor Y | CONPOSY | 0x02
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* 8-bit unsigned number
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* Read/Write
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### Width | CONX | 0x03
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* 8-bit unsigned number
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* Read/Write
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### Height | CONY | 0x04
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* 8-bit unsigned number
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* Read/Write
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## Interrupts/Faults | 0x1*
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Faults can be caught and handled by specifying a jump location in FLTRH and FLTRL. This handler must clear FLTSYS/2, it may call RET to continue execution or jump elsewhere.
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### Fault Status | FLTSTS | 0x10
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| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
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| --------------- | --- | --- | --------------- | --------------- | ---------- | ------------ | ---- | --- |
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| **Read/Write** | | | R | R | R | R | R/W | R/W |
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| **Default ** | | | X | X | X | X | X | 0 |
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| **Name** | | | Memory Overflow | Stack Exceeded | Illegal Op | Undefined Op | Trip | Enabled |
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If not enabled, the system will halt should a fault occur.
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In a fault condition, only one type will be indicated.
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Clearing **Trip** will clear status bits 3-8, it cannot be set.
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If a second fault occurs before trip is cleared, the system will halt; this known as a double-fault.
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**Undefined Op** indicates an operation that was unknown. **Illegal Op** indicates that the parameters to the operation were not valid.
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**Stack Exceeded** Indicates that the stack either overflowed (PUSH or CALL when full) or underflowed (RET or POP when empty).
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### Fault Routine High Byte | FLTJH | 0x11
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The high byte of the fault handler jump.
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### Fault Routine Low Byte | FLTJL | 0x12
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The low byte of the fault handler jump.
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## ALU | 0x2*
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Flags here for logic/math results
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## Tape | 0x3*
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Tape control and status
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<!--
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### Name | ALIAS | 0x00
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| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
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| --------------- | --- | --- | --- | --- | --- | --- | --- | --- |
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| **Read/Write** | | | | | | | | |
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| **Default ** | | | | | | | | |
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| **Name** | | | | | | | | |
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--> |