Hardware Timers: Difference between revisions
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The PSVita system embeds 8 Word timers (<code>SceWT0</code> to <code>SceWT7</code>) and 6 Longrange timers (<code>SceLT0</code> to <code>SceLT5</code>). The timers | The PSVita system embeds 8 Word timers (<code>SceWT0</code> to <code>SceWT7</code>) and 6 Longrange timers (<code>SceLT0</code> to <code>SceLT5</code>). The timers consist of a counter that gets incremented at a fixed time interval, and can generate an interrupt when a certain value is reached. | ||
Most timers are managed by [[SceSystimer]]. | Most timers are managed by [[SceSystimer]]. | ||
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== Word Timers == | == Word Timers == | ||
Timers with 32-bit counters. | Timers with 32-bit counters, incremented at an unknown frequency (seems to be in the order of ns). | ||
<source lang="C"> | <source lang="C"> | ||
typedef volatile _SceWordTimer { | typedef volatile _SceWordTimer { | ||
SceUInt32 unk0; // Value at which an interrupt is triggered? | SceUInt32 unk0; // Value at which an interrupt is triggered? | ||
SceUInt32 | SceUInt32 current; // Current value of the timer's counter | ||
SceUInt32 | SceUInt32 cfg; // Configuration register | ||
SceUInt32 unkC; // Another counter? | SceUInt32 unkC; // Another counter? | ||
SceUInt32 unk10; // Unused? | SceUInt32 unk10; // Unused? | ||
SceUInt32 unk14; // Write 0x3 to clear | SceUInt32 unk14; // Interrupt status? Write 0x3 to clear pending IRQ? | ||
} SceWordTimer; | } SceWordTimer; | ||
</source> | </source> | ||
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== Long Timers == | == Long Timers == | ||
Timers with 64-bit counters. | Timers with 64-bit counters. SceLT5 timer is incremented every microsecond (1MHz frequency). | ||
<source lang="C"> | <source lang="C"> | ||
typedef volatile _SceLongTimer { | typedef volatile _SceLongTimer { | ||
SceKernelSysClock | SceKernelSysClock current; // Current value of the timer counter | ||
SceKernelSysClock unk8; // Value at which an interrupt is triggered? | SceKernelSysClock unk8; // Value at which an interrupt is triggered? | ||
SceKernelSysClock unk10; // Another counter? | SceKernelSysClock unk10; // Another counter? | ||
SceUInt32 unk18; // Write 0x3 to clear | SceUInt32 unk18; // Interrupt status? Write 0x3 to clear pending IRQ? | ||
SceUInt32 | SceUInt32 cfg; // Configuration register | ||
} SceLongTimer; | } SceLongTimer; | ||
</source> | </source> | ||
Revision as of 14:45, 13 July 2022
The PSVita system embeds 8 Word timers (SceWT0 to SceWT7) and 6 Longrange timers (SceLT0 to SceLT5). The timers consist of a counter that gets incremented at a fixed time interval, and can generate an interrupt when a certain value is reached.
Most timers are managed by SceSystimer.
Available timers
The Address column indicates the physical address at which the interface for a timer is located.
Each timer interface takes 0x1000 bytes.
| Name | Address | Interrupt ID | Usage |
|---|---|---|---|
| SceLT0 / SceSystimerLongrangeTimer0 | 0xE20B1000 | 0x88 | Available for SceSystimer |
| SceLT1 / SceSystimerLongrangeTimer1 | 0xE20B2000 | 0x89 | Available for SceSystimer |
| SceLT2 / SceSystimerLongrangeTimer2 | 0xE20B3000 | 0x8A | Available for SceSystimer |
| SceLT3 / SceSystimerLongrangeTimer3 | 0xE20B4000 | 0x8B | Available for SceSystimer |
| SceLT4 / SceSystimerLongrangeTimer4 | 0xE20B5000 | 0x8C | Available for SceSystimer |
| SceLT5 | 0xE20B6000 | 0x8D | Used by SceKernelThreadMgr as CPU timer |
| SceWT0 / SceSystimerWordTimer0 | 0xE20B7000 | 0x80 | Available for SceSystimer |
| SceWT1 / SceSystimerWordTimer1 | 0xE20B8000 | 0x81 | Available for SceSystimer |
| SceWT2 / SceSystimerWordTimer2 | 0xE20B9000 | 0x82 | Available for SceSystimer |
| SceWT3 / SceSystimerWordTimer3 | 0xE20BA000 | 0x83 | Available for SceSystimer |
| SceWT4 / SceSystimerWordTimer4 | 0xE20BB000 | 0x84 | Available for SceSystimer |
| SceWT5 / SceSystimerWordTimer5 | 0xE20BC000 | 0x85 | Available for SceSystimer |
| SceWT6 / SceSystimerWordTimer6 | 0xE20BD000 | 0x86 | Available for SceSystimer |
| SceWT7 / SceTimerForUsleep | 0xE20BE000 | 0x87 | Used by Tzs SceKernelIntrMgr for usleep - ?may be accessible in Secure state only? |
Word Timers
Timers with 32-bit counters, incremented at an unknown frequency (seems to be in the order of ns).
typedef volatile _SceWordTimer {
SceUInt32 unk0; // Value at which an interrupt is triggered?
SceUInt32 current; // Current value of the timer's counter
SceUInt32 cfg; // Configuration register
SceUInt32 unkC; // Another counter?
SceUInt32 unk10; // Unused?
SceUInt32 unk14; // Interrupt status? Write 0x3 to clear pending IRQ?
} SceWordTimer;
Long Timers
Timers with 64-bit counters. SceLT5 timer is incremented every microsecond (1MHz frequency).
typedef volatile _SceLongTimer {
SceKernelSysClock current; // Current value of the timer counter
SceKernelSysClock unk8; // Value at which an interrupt is triggered?
SceKernelSysClock unk10; // Another counter?
SceUInt32 unk18; // Interrupt status? Write 0x3 to clear pending IRQ?
SceUInt32 cfg; // Configuration register
} SceLongTimer;
NOTE: on the PSVita CPU, 64-bit accesses are not guaranteed to be atomic. This can lead to issues when reading the timer if the low word of a counter is about to overflow. To ensure the readings from a timer are accurate, use code similar to the following code:
//Return value should hopefully be optimized into registers
SceKernelSysClock readCounter(volatile SceKernelSysClock* pTimerCounter) {
SceKernelSysClock ctr;
SceUInt32 ctrHi;
do {
ctr.hi = pTimeCounter->hi; //Read high word first
ctr.lo = pTimeCounter->lo; //Read low word next
ctrHi = pTimeCounter->hi; //Read high word again to make sure no overflow happened
} while (timerVal.hi != timerValHi); //Try again if high word changed while reading low word
return ctr;
}
Configuration register
The configuration register bit mappings seems to be identical for Word and Long timers.
| Timer | Value | Behaviour/notes |
|---|---|---|
| SceLT5 | 0x2F34500D | Interrupt fired when counter reaches threshold |
| Mask | Effect | Notes |
|---|---|---|
| 0x00000001 | Counting enable | 0x0 = timer stopped, 0x1 = timer counting |
| 0x0000000E | ? | |
| 0x00000070 | ? | ?Mode select? |
| 0x00000080 | ? | |
| 0x00000700 | ? | |
| 0x00000800 | ? | Unused? |
| 0x0000F000 | ? | |
| 0x000F0000 | ? | |
| 0x00F00000 | ? | |
| 0xFF000000 | ? |