JAJS280O October 2003 – March 2019 TMS320F2801 , TMS320F28015 , TMS320F28016 , TMS320F2802 , TMS320F2806 , TMS320F2808 , TMS320F2809
PRODUCTION DATA.
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The 280x devices have 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) | SYSCLKOUT
(CLKIN)(2) |
---|---|
0000 (PLL bypass) | OSCCLK/n |
0001 | (OSCCLK*1)/n |
0010 | (OSCCLK*2)/n |
0011 | (OSCCLK*3)/n |
0100 | (OSCCLK*4)/n |
0101 | (OSCCLK*5)/n |
0110 | (OSCCLK*6)/n |
0111 | (OSCCLK*7)/n |
1000 | (OSCCLK*8)/n |
1001 | (OSCCLK*9)/n |
1010 | (OSCCLK*10)/n |
1011–1111 | Reserved |
NOTE
PLLSTS[CLKINDIV] enables or bypasses the divide-by-two block before the clock is fed to the core. This bit must be 0 before writing to the PLLCR and must only be set after PLLSTS[PLLLOCKS] = 1.
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 |