SPRS357D August 2006 – June 2020 TMS320F28044
PRODUCTION DATA.
Refer to the PDF data sheet for device specific package drawings
The F28044 device has an on-chip, PLL-based clock module. This module provides all the necessary clocking signals for the device, as well as control for low-power mode entry. The PLL has a 4-bit ratio control PLLCR[DIV] to select different CPU clock rates. The watchdog module should be disabled before writing to the PLLCR register. It can be re-enabled (if need be) after the PLL module has stabilized, which takes 131072 OSCCLK cycles.
PLLCR[DIV](1) | PLLSTS[CLKINDIV] | SYSCLKOUT
(CLKIN)(2) |
---|---|---|
0000 (PLL bypass) | 0 | OSCCLK/2 |
0000 (PLL bypass) | 1 | OSCCLK |
0001 | 0 | (OSCCLK*1)/2 |
0010 | 0 | (OSCCLK*2)/2 |
0011 | 0 | (OSCCLK*3)/2 |
0100 | 0 | (OSCCLK*4)/2 |
0101 | 0 | (OSCCLK*5)/2 |
0110 | 0 | (OSCCLK*6)/2 |
0111 | 0 | (OSCCLK*7)/2 |
1000 | 0 | (OSCCLK*8)/2 |
1001 | 0 | (OSCCLK*9)/2 |
1010 | 0 | (OSCCLK*10)/2 |
1011–1111 | 0 | Reserved |
NOTE
PLLSTS[CLKINDIV] can be set to 1 only if PLLCR is 0x0000. PLLCR should not be changed once PLLSTS[CLKINDIV] is set.
The PLL-based clock module provides two modes of operation:
PLL MODE | REMARKS | PLLSTS[CLKINDIV] | SYSCLKOUT
(CLKIN) |
---|---|---|---|
PLL Off | Invoked by the user setting the PLLOFF bit in the PLLSTS register. The PLL block is disabled in this mode. This can be useful to reduce system noise and for low power operation. The PLLCR register must first be set to 0x0000 (PLL Bypass) before entering this mode. The CPU clock (CLKIN) is derived directly from the input clock on either X1/X2, X1 or XCLKIN. | 0 | OSCCLK/2 |
1 | OSCCLK | ||
PLL Bypass | PLL Bypass is the default PLL configuration upon power-up or after an external reset (XRS). This mode is selected when the PLLCR register is set to 0x0000 or while the PLL locks to a new frequency after the PLLCR register has been modified. In this mode, the PLL itself is bypassed but the PLL is not turned off. | 0 | OSCCLK/2 |
1 | OSCCLK | ||
PLL Enable | Achieved by writing a non-zero value n into the PLLCR register. Upon writing to the PLLCR the device will switch to PLL Bypass mode until the PLL locks. | 0 | OSCCLK*n/2 |