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Clock Domains
4.2.4 I/O Domains
The I/O domains refer to the frequencies of the peripherals that communicate through device pins. In many cases, there are frequency requirements for a peripheral pin interface that are set by an outside standard and must be met. It is not necessarily possible to obtain these frequencies from the
Table
Table 4-5. Peripheral I/O Domain Clock
| I/O Domain Clock | I/O (External) Domain Clock Source Options |
| |
|
|
|
| |
Peripheral | Frequency | Internal Clock Source | External Clock Source | Core Clock Domain |
DDR2 | PLLC2 SYSCLK1 | — | CLKDIV3 | |
VPFE | — | PCLK | CLKDIV3 | |
VPBE | PLLC1 SYSCLKBP | VPBECLK | CLKDIV3 | |
|
| (typically 27 MHZ) |
|
|
|
| PLLC2 SYSCLK2 | PCLK |
|
|
| (typically 54 MHZ) |
|
|
PCI | 33 MHZ | — | PCICLK | CLKDIV3 |
EMAC | 25 MHZ | — | MTXCLK, MRXCLK | CLKDIV6 |
VLYNQ | up to 80 MHZ | PLLC1 SYSCLK3 | VLYNQ_CLOCK | CLKDIV6 |
McBSP | up to 40 MHZ | PLLC1 SYSCLK3 | CLKS, CLKX, CLKR | CLKDIV6 |
McASP | up to 40 MHZ | PLLC1 SYSCLK3 | AHCLKX, AHCLKR, | CLKDIV6 |
|
|
| ACLKX, ACLKR |
|
GPIO | NA (asynchronous | — | — | CLKDIV6 |
| interface) |
|
|
|
EMIFA | NA (asynchronous | — | — | CLKDIV6 |
| interface) |
|
|
|
HPI | NA (asynchronous | — | — | CLKDIV6 |
| interface) |
|
|
|
I2C | up to 400 kHz | MXI/CLKIN | SCL | CLKIN |
|
| (typically 27 MHZ) |
|
|
Timer | output up to 1/2 CLKIN | MXI/CLKIN | TINP0L (Timer 0), | CLKIN |
| frequency | (typically 27 MHZ) | TINP1L (Timer 1) |
|
| input up to 1/4 CLKIN |
|
|
|
| frequency |
|
|
|
Watchdog Timer | NA | MXI/CLKIN | — | CLKIN |
|
| (typically 27 MHZ) |
|
|
PWM | NA | — | — | CLKIN |
UART | NA | — | — | CLKIN |
HECC | NA | — | — | CLKIN |
34 | Device Clocking | |
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