mirror of
https://github.com/RfidResearchGroup/proxmark3.git
synced 2024-12-28 03:14:53 +08:00
215 lines
5.9 KiB
Markdown
215 lines
5.9 KiB
Markdown
<a id="Top"></a>
|
|
|
|
# Notes on device side clocks
|
|
The device side firmware uses a range of different clocks. Here is an attempt to document the clocks in use and for what they are used.
|
|
|
|
|
|
# Table of Contents
|
|
- [Notes on device side clocks](#notes-on-device-side-clocks)
|
|
- [Table of Contents](#table-of-contents)
|
|
- [Units](#units)
|
|
- [Slow clock](#slow-clock)
|
|
- [Main Oscillator / MAINCK](#main-oscillator--mainck)
|
|
- [PLL clock](#pll-clock)
|
|
- [Master Clock MCK, Processor Clock PCK, USB clock UDPCK](#master-clock-mck-processor-clock-pck-usb-clock-udpck)
|
|
- [Peripheral clocks](#peripheral-clocks)
|
|
- [1 kHz RTC: TickCount functions](#1-khz-rtc-tickcount-functions)
|
|
- [Occasional PWM timer](#occasional-pwm-timer)
|
|
- [Occasional TC0+TC1 / CountUS functions](#occasional-tc0tc1--countus-functions)
|
|
- [Occasional TC0+TC1+TC2 SSP\_CLK from FPGA / CountSspClk functions](#occasional-tc0tc1tc2-ssp_clk-from-fpga--countsspclk-functions)
|
|
- [Occasional TC0+TC1 / Ticks functions](#occasional-tc0tc1--ticks-functions)
|
|
|
|
|
|
## Units
|
|
^[Top](#top)
|
|
|
|
Good calculator
|
|
https://www.unitjuggler.com/convert-frequency-from-MHz-to-ns(p).html?val=3.39
|
|
|
|
Basic units of time measurment or how long in time is a Hertz?
|
|
|
|
```
|
|
1 hertz = 1 second = 1000 milli seconds
|
|
10 Hertz = 1 / 10 = 0,1 = 100 milli seconds
|
|
100 Hertz = 1 / 100 = 0,01 = 10 milli seconds
|
|
1 kHz = 1 / 1000 = 0,001 = 1 milli seconds
|
|
10 kHz = 1 / 10 000 = 0,000 1 = 100 micro seconds
|
|
100 kHz = 1 / 100 000 = 0,000 01 = 10 micro seconds
|
|
1 MHZ = 1 / 1 000 000 = 0,000 001 = 1 micro seconds
|
|
```
|
|
|
|
- kHz, Kilo Hertz, 1000 Hertz
|
|
- MHz, Mega Hertz, 1000 000 Hertz
|
|
|
|
|
|
Basic units of time you will run into in the RFID world.
|
|
|
|
```
|
|
13.56 MHz = 1 / 13 560 000 = 73,74 nano seconds = 0,07374 micro seconds
|
|
125 kHz = 1/ 125 000 = 8 micro seconds
|
|
```
|
|
|
|
Given these units the following clocks used by Proxmark3 will make more sense.
|
|
|
|
Like the SSP Clock running at 3.39 MHz.
|
|
3.39 MHz = 1 / 3 390 000 = 294,98 nano seconds = 0,2949 micro seconds
|
|
|
|
1 tick at 3.39 MHz is 294.98 nano seconds.
|
|
|
|
|
|
|
|
## Slow clock
|
|
^[Top](#top)
|
|
|
|
~32kHz internal RC clock
|
|
|
|
Can be between 22 and 42 kHz
|
|
|
|
## Main Oscillator / MAINCK
|
|
^[Top](#top)
|
|
|
|
cf `PMC_MOR` register
|
|
|
|
16 MHz, based on external Xtal
|
|
|
|
## PLL clock
|
|
^[Top](#top)
|
|
|
|
cf `PMC_PLLR` register
|
|
|
|
96 MHz (MAINCK * 12 / 2)
|
|
|
|
## Master Clock MCK, Processor Clock PCK, USB clock UDPCK
|
|
^[Top](#top)
|
|
|
|
cf `common_arm/clocks.c`
|
|
|
|
cf `PMC_MCKR` and `PMC_SCER` registers
|
|
|
|
* MCK starts with RC slow clock (22 to 42 kHz).
|
|
* Then MCK configured from PLL: 48 MHz (PLL / 2)
|
|
|
|
cf `bootrom.c`:
|
|
|
|
PCK can be disabled to enter idle mode, but on Proxmark3 it's always on, so PCK is also 48 MHz.
|
|
|
|
USB need to be clocked at 48 MHz from the PLL, so PLL / 2 (cf `CKGR_PLLR`).
|
|
|
|
|
|
## Peripheral clocks
|
|
^[Top](#top)
|
|
|
|
cf `bootrom.c`:
|
|
|
|
Distribute MCK/PCK? clock to Parallel I/O controller, ADC, SPI, Synchronous Serial controller, PWM controller, USB.
|
|
|
|
cf `appmain.c`
|
|
|
|
Activate PCK0 pin as clock output, based on PLL / 4 = 24 MHz, for the FPGA.
|
|
|
|
## 1 kHz RTC: TickCount functions
|
|
^[Top](#top)
|
|
|
|
cf `armsrc/ticks.c`
|
|
|
|
cf `PMC_MCFR` and `RTTC_RTMR` registers for configuration, `RTTC_RTVR` register for reading value.
|
|
|
|
Characteristics:
|
|
|
|
* 1 kHz, 32b (49 days), if used with 16b: 65s
|
|
* Configured at boot (or TIA) with `StartTickCount()`
|
|
* Time events with `GetTickCount()`/`GetTickCountDeltaDelta()`, see example
|
|
* Coarse, based on the ~32kHz RC slow clock with some adjustment factor computed by TIA
|
|
* Maybe 2.5% error, can increase if temperature conditions change and no TIA is recomputed
|
|
* If TimingIntervalAcquisition() is called later, StartTickCount() is called again and RTC is reset
|
|
|
|
Usage:
|
|
|
|
```
|
|
uint32_t ti = GetTickCount();
|
|
...do stuff...
|
|
uint32_t delta = GetTickCountDelta(ti);
|
|
```
|
|
|
|
Current usages:
|
|
|
|
* cheap random for nonces, e.g. `prng_successor(GetTickCount(), 32)`
|
|
* rough timing of some operations, only for informative purposes
|
|
* timeouts
|
|
* USB connection speed measure
|
|
|
|
## Occasional PWM timer
|
|
^[Top](#top)
|
|
|
|
* `void SpinDelayUs(int us)`
|
|
* `void SpinDelay(int ms)` based on SpinDelayUs
|
|
* `void SpinDelayUsPrecision(int us)`
|
|
|
|
Busy wait based on 46.875 kHz PWM Channel 0
|
|
|
|
* 21.3 us precision and maximum 1.39 s
|
|
* *Precision* variant: 0.7 us precision and maximum 43 ms
|
|
|
|
## Occasional TC0+TC1 / CountUS functions
|
|
^[Top](#top)
|
|
|
|
cf `armsrc/ticks.c`
|
|
|
|
About 1 us precision
|
|
|
|
* `void StartCountUS(void)`
|
|
* `uint32_t RAMFUNC GetCountUS(void)`
|
|
|
|
Use two chained timers TC0 and TC1.
|
|
TC0 runs at 1.5 MHz and TC1 is clocked when TC0 reaches 0xC000.
|
|
|
|
Maximal value: 0x7fffffff = 2147 s
|
|
|
|
Can't be used at the same time as CountSspClk or Ticks functions.
|
|
|
|
## Occasional TC0+TC1+TC2 SSP_CLK from FPGA / CountSspClk functions
|
|
^[Top](#top)
|
|
|
|
cf `armsrc/ticks.c`
|
|
|
|
About 1 cycle of 13.56 MHz? precision
|
|
|
|
* `void StartCountSspClk(void)`
|
|
* `void ResetSspClk(void)`
|
|
* `uint32_t RAMFUNC GetCountSspClk(void)`
|
|
* `uint32_t RAMFUNC GetCountSspClkDelta(uint32_t start)` <= **TODO** could be used more often
|
|
|
|
Use two chained timers TC0 and TC1.
|
|
TC0 runs at SSP_CLK from FPGA (13.56 MHz?) and TC1 is clocked when TC0 loops.
|
|
|
|
Usage:
|
|
|
|
* for iso14443 commands to count field cycles
|
|
* Also usable with FPGA in LF mode ?? cf `armsrc/legicrfsim.c` SSP Clock is clocked by the FPGA at 212 kHz (sub-carrier frequency)
|
|
|
|
Can't be used at the same time as CountUS or Ticks functions.
|
|
|
|
## Occasional TC0+TC1 / Ticks functions
|
|
^[Top](#top)
|
|
|
|
cf `armsrc/ticks.c`
|
|
|
|
1.5 MHz
|
|
|
|
* `void StartTicks(void)`
|
|
* `uint32_t GetTicks(void)` <= **TODO** why no GetTicksDelta ?
|
|
* `void WaitTicks(uint32_t ticks)`
|
|
* `void WaitUS(uint32_t us)`
|
|
* `void WaitMS(uint32_t ms)`
|
|
* `void StopTicks(void)` <= **TODO** why a stop for this timer and not for CountUS / CountSspClk ?
|
|
|
|
Use two chained timers TC0 and TC1.
|
|
TC0 runs at 1.5 MHz and TC1 is clocked when TC0 loops.
|
|
|
|
Maximal value: 0xffffffff = 2863 s (but don't use high value with WaitTicks else you'll trigger WDT)
|
|
|
|
Usage:
|
|
|
|
* Timer for bitbanging, or LF stuff when you need a very precise timer
|
|
|
|
Can't be used at the same time as CountUS or CountSspClk functions.
|