Hardware Timers: Difference between revisions
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| SceLT4 / SceSystimerLongrangeTimer4 || 0xE20B5000 || 0x8C || Available for [[SceSystimer]] | | SceLT4 / SceSystimerLongrangeTimer4 || 0xE20B5000 || 0x8C || Available for [[SceSystimer]] | ||
|- | |- | ||
| SceLT5 || 0xE20B6000 || 0x8D || Used by [[SceKernelThreadMgr]] as CPU timer | | SceLT5 / SceThreadmgrTimer || 0xE20B6000 || 0x8D || Used by [[SceKernelThreadMgr]] as CPU timer | ||
|- | |- | ||
| SceWT0 / SceSystimerWordTimer0 || 0xE20B7000 || 0x80 || Available for [[SceSystimer]] | | SceWT0 / SceSystimerWordTimer0 || 0xE20B7000 || 0x80 || Available for [[SceSystimer]] |
Revision as of 19:09, 13 August 2023
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 configurable time interval (multiple of a base frequency?), 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 |
---|---|---|---|
? | 0xE20B0000 | ? | Never used by the operating system |
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 / SceThreadmgrTimer | 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 |
Misc Reg
Miscellaneous features related to all timers can be accessed from an interface at physical address 0xE20BF000
.
Offset | Usage |
---|---|
0x0 | Bus Error Address |
0x4 | Bus Error Attributes |
0x8 | Secure Bus Error Address |
0xC | Secure Bus Error Attributes |
Configuration register
The configuration register is identical for all timers. The period of a Systimer tick is calculated using the following formulas:
t = (prescale_factor + 1) / src_clk
in seconds (multiply by 10^9 for ns)f = 1 / t = src_clk / (prescale_factor+1)
in Hz (divide by 10^6 for MHz)
src_clk
is the frequency of the timer's input clock - see below for more information.
Mask | Name | Effect / Notes |
---|---|---|
0x00000001 | enable | 0: timer stopped - 1: timer counting |
0x0000000E | ? | |
0x00000070 | ? | ?Mode select? |
0x00000080 | ? | |
0x00000700 | clk2_ctrl | Changes clock if clk_select == 2
|
0x00000800 | RAZ/WI | Read As Zero / Write Ignore (always 0) |
0x0000F000 | ? | |
0x000F0000 | ? | |
0x00F00000 | clk_select | Controls which clock is used as input to prescaler (see below) |
0xFF000000 | prescale_factor | Input clock division factor (the higher this is, the slower the timer will tick) |
clk_select |
Input clock | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0 | ScePower SysClock (190/222MHz) | ||||||||||||
1 | ~37MHz | ||||||||||||
2 | Varies based on clk2_ctrl
| ||||||||||||
3 | 48MHz | ||||||||||||
4 | 60Hz | ||||||||||||
5 | ~35.6kHz | ||||||||||||
8 | 60Hz | ||||||||||||
9 | ~45kHz | ||||||||||||
6-7,A-F | No clock (timer doesn't tick) |
Timer | Value | Explaination |
---|---|---|
SceWT7 (SceTimerForUsleep) | 0xDD00000D | SysClock source / (prescale_factor = 221) -> 0.85/1MHz frequency |
SceLT5 | 0x2F34500D | 48MHz source / (prescale_factor = 47) -> 1MHz frequency |
Word Timers
Timers with 32-bit counters.
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 configured to increment 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 ARMv7 processors that do not support the Large Physical Address Extension, such as the PS Vita's 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* pTimer) { SceKernelSysClock ctr; SceUInt32 ctrHi; do { ctr.u.hi = pTimer->u.hi; //Read high word first ctr.u.lo = pTimer->u.lo; //Read low word next ctrHi = pTimer->u.hi; //Read high word again to make sure no overflow happened } while (ctr.hi != ctrHi); //Try again if high word changed while reading low word return ctr; }
Top Timer
Located at physical address 0xE20B0000
. Called like this because it's the first one in Timer memory region.
The Top timer is a 64-bit timer with the following restrictions:
- Cannot change the input clock (always SysClock)
- Doesn't support configuration other than prescale factor
- All fields other than
prescale_factor
andenable
are RAZ/WI in this timer's configuration register
- All fields other than
- Cannot generate interrupts?
typedef volatile _SceTopTimer { SceKernelSysClock current; // Current value of the timer counter unsigned RAZ_WI; //Read As Zero / Write Ignore SceUInt32 cfg; //Configuration register } SceHiddenTimer;