Hi Friends, I am new in this of MSP430, and i am trying to do something with TIMERB that i don't know if this could be posible. Until now i couldn't do it. I am working with F169 at 8Mhz I would like to do send out like a clock of 500Khz but without interrupt. It is done is easy. The hard part it is that i need a 500hz interrupt timer inside and if could be posible send out too. This part doesn't work in any way. Have any one made something like that. I saw the examples and saw that it could be done but the frecuencies are more similar 2000,200, 40, 6hz Thanks in advance __________________________________________________ Correo Yahoo! Espacio para todos tus mensajes, antivirus y antispam gratis! Abrtu cuenta ya! - http://correo.yahoo.com.ar
About timers
Started by ●April 10, 2006
Reply by ●April 10, 20062006-04-10
Hi Juan, One possibility perhaps is this : 1. 500 kHz You can output all system clocks, but only at fixed pins. So if you don't need another clock such as 32.768 kHz, and can afford to set SMCLK to 1, 2 or 4 MHz (in the example of 8 MHz crystal), then you can output the SMCLK of 1/2/4 MHz on the reserved SMCLK pin. Now route this - DC coupled - to the XIN pin, and leave XOUT open (ie. LFXTAL in/out). Now you can nominate the ACLK signal to be a divided SMCLK . These would be the settings with 8 MHz: SMCLK = Div/2 = 4 MHz => ACLK = XIN/8 = 500 kHz. SMCLK = Div/4 = 2 MHz => ACLK = XIN/4 = 500 kHz. SMCLK = Div/8 = 1 MHz => ACLK = XIN/2 = 500 kHz. Now set the reserved ACLK pin to output the 500 kHz signal and voila. Note that for most cases, MCLK (your CPU clock) doesn't need to be precise and can be the DCO running at up to max. speed. (~ 9.5 - 10 MHz with ext res). Also note that if your crystal is for example 4 MHz, then you don't need to route SMCLK to XIN, since 4 MHz / 8 = 500 kHz. Just output SMCLK as 500 kHz then. These choices depend on what clock signals you will need, and whether you can allow for that. (also, current will be slightly higher) NOTE : if you do this on a 44X family part, make sure you RESET the fault flag for the externally generated input to the XIN pin after init of XT2.... otherwise it won't generate ACLK !!!! 2. 500 Hz interrupt You can use TIMERB in UP mode. Set the output unit to toggle at a compare event on any Timer_B channel you want, and that channel's compare unit CCRBx value to the appropriate value to generate 500 Hz. The output unit will toggle the corresponding CCRBx pin, and if you want you can enable the proper interrupt for it too (although you don't have to, to output the 500 Hz signal). The 500 kHz solution depends on whether you can set up the SMCLK, ACLK and MCLK to function that way... ! Note that it will take more current to externally generate a 500 kHz signal if you really need it. B rgds Kris -----Original Message----- From: msp430@msp4... [mailto:msp430@msp4...] On Behalf Of Ing juan manuell Sent: Tuesday, 11 April 2006 2:19 AM To: msp430 Subject: [msp430] About timers Hi Friends, I am new in this of MSP430, and i am trying to do something with TIMERB that i don't know if this could be posible. Until now i couldn't do it. I am working with F169 at 8Mhz I would like to do send out like a clock of 500Khz but without interrupt. It is done is easy. The hard part it is that i need a 500hz interrupt timer inside and if could be posible send out too. This part doesn't work in any way. Have any one made something like that. I saw the examples and saw that it could be done but the frecuencies are more similar 2000,200, 40, 6hz Thanks in advance __________________________________________________ Correo Yahoo! Espacio para todos tus mensajes, antivirus y antispam gratis! Abrtu cuenta ya! - http://correo.yahoo.com.ar . Yahoo! Groups Links
Reply by ●April 11, 20062006-04-11
Thanks i will try it. Microbit <microbit@micr...> escribi Hi Juan, One possibility perhaps is this : 1. 500 kHz You can output all system clocks, but only at fixed pins. So if you don't need another clock such as 32.768 kHz, and can afford to set SMCLK to 1, 2 or 4 MHz (in the example of 8 MHz crystal), then you can output the SMCLK of 1/2/4 MHz on the reserved SMCLK pin. Now route this - DC coupled - to the XIN pin, and leave XOUT open (ie. LFXTAL in/out). Now you can nominate the ACLK signal to be a divided SMCLK . These would be the settings with 8 MHz: SMCLK = Div/2 = 4 MHz => ACLK = XIN/8 = 500 kHz. SMCLK = Div/4 = 2 MHz => ACLK = XIN/4 = 500 kHz. SMCLK = Div/8 = 1 MHz => ACLK = XIN/2 = 500 kHz. Now set the reserved ACLK pin to output the 500 kHz signal and voila. Note that for most cases, MCLK (your CPU clock) doesn't need to be precise and can be the DCO running at up to max. speed. (~ 9.5 - 10 MHz with ext res). Also note that if your crystal is for example 4 MHz, then you don't need to route SMCLK to XIN, since 4 MHz / 8 = 500 kHz. Just output SMCLK as 500 kHz then. These choices depend on what clock signals you will need, and whether you can allow for that. (also, current will be slightly higher) NOTE : if you do this on a 44X family part, make sure you RESET the fault flag for the externally generated input to the XIN pin after init of XT2.... otherwise it won't generate ACLK !!!! 2. 500 Hz interrupt You can use TIMERB in UP mode. Set the output unit to toggle at a compare event on any Timer_B channel you want, and that channel's compare unit CCRBx value to the appropriate value to generate 500 Hz. The output unit will toggle the corresponding CCRBx pin, and if you want you can enable the proper interrupt for it too (although you don't have to, to output the 500 Hz signal). The 500 kHz solution depends on whether you can set up the SMCLK, ACLK and MCLK to function that way... ! Note that it will take more current to externally generate a 500 kHz signal if you really need it. B rgds Kris -----Original Message----- From: msp430@msp4... [mailto:msp430@msp4...] On Behalf Of Ing juan manuell Sent: Tuesday, 11 April 2006 2:19 AM To: msp430 Subject: [msp430] About timers Hi Friends, I am new in this of MSP430, and i am trying to do something with TIMERB that i don't know if this could be posible. Until now i couldn't do it. I am working with F169 at 8Mhz I would like to do send out like a clock of 500Khz but without interrupt. It is done is easy. The hard part it is that i need a 500hz interrupt timer inside and if could be posible send out too. This part doesn't work in any way. Have any one made something like that. I saw the examples and saw that it could be done but the frecuencies are more similar 2000,200, 40, 6hz Thanks in advance __________________________________________________ Correo Yahoo! Espacio para todos tus mensajes, antivirus y antispam gratis! Abrtu cuenta ya! - http://correo.yahoo.com.ar . . --------------------------------- __________________________________________________ Correo Yahoo! Espacio para todos tus mensajes, antivirus y antispam gratis! Abrtu cuenta ya! - http://correo.yahoo.com.ar
