PropBasic- \CLKSET and BAUD

camelot2

What I want to do is run a program at a system freq of 100MHz, send some
data to the serial terminal then change the system freq to 50MHZ and send
some more data to the serial terminal then end. When I run the following
program the serial terminal displays
Dave1_
`0?<x?f<??
and not
Dave1
Dave2
It seems that when the system freq is changed the BAUD is not adjusted
correctly. How do you change the system freq and have a correct BAUD???
Here is the program - thanks for your help - Dave

' Device Settings
'

---

DEVICE P8X32A, XTAL1, PLL16X
XIN 6_250_000
'

---

Baud CON "T9600"
CR CON 13
'

---

' I/O Pins
'

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RX PIN 31 INPUT
TX PIN 30 HIGH ' set to idle (true)
'

---

' Cog Variables (Long only)
'

---

NewFreq VAR LONG
'

---

' SUB/FUNC Definitions
'

---

' ======================================================================
PROGRAM Start
' ======================================================================
Start:
SEROUT 30, Baud, "Dave1"
SEROUT 30, Baud, CR
NewFreq = %01101110 'set the clk to PLL8X
\CLKSET NewFreq 'system clk should now be 50MHz ???
PAUSE 1000 'pause 1000ms
SEROUT 30, BAUD , "Dave2"
END

kwinn

Not surprising the baud rate is not adjusted when the clock frequency changes. The serial data objects calculate a timing constant at startup using the initial clock frequency and desired baud rate. You need to calculate the correct timing constant for the new clock frequency.

camelot2

thanks kwinn , how do I do this calculation - thanks again - Dave

camelot2

hi again, could someone please show me how to do the calculation mentioned by kwinn
thanks for your help - Dave

Bean

The baud calculation is a constant. You cannot change it.
Just use twice the baud rate when you change to 50MHz.

' Device Settings
' ----------------------------------------------------------------------
DEVICE P8X32A, XTAL1, PLL16X
XIN 6_250_000
' ----------------------------------------------------------------------
Baud100 CON "T9600"
Baud50  CON "T19200"
CR CON 13
' ----------------------------------------------------------------------
' I/O Pins
' ----------------------------------------------------------------------
RX PIN 31 INPUT
TX PIN 30 HIGH ' set to idle (true)
' ----------------------------------------------------------------------
' Cog Variables (Long only)
' ----------------------------------------------------------------------
NewFreq VAR LONG
' ----------------------------------------------------------------------
' SUB/FUNC Definitions
' ----------------------------------------------------------------------
' ================================================== ====================
PROGRAM Start
' ================================================== ====================
Start:
SEROUT 30, Baud100, "Dave1"
SEROUT 30, Baud100, CR
NewFreq = %01101110 'set the clk to PLL8X
\CLKSET NewFreq 'system clk should now be 50MHz ???
PAUSE 500 'pause 1000ms
SEROUT 30, BAUD50 , "Dave2"
END 

Bean