MC9S08DN60_08 Datasheet, PDF (282/356 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 15 Timer/PWM Module (S08TPMV3)
BDM mode returns the latched value of TPMxCNTH:L from the read buffer instead of the
frozen TPM counter value.
— This read coherency mechanism is cleared in TPM v3 in BDM mode if there is a write to
TPMxSC, TPMxCNTH or TPMxCNTL. Instead, in these conditions the TPM v2 does not clear
this read coherency mechanism.
3. Read of TPMxCnVH:L registers (Section 15.3.5, “TPM Channel Value Registers
(TPMxCnVH:TPMxCnVL))
— In TPM v3, any read of TPMxCnVH:L registers during BDM mode returns the value of the
TPMxCnVH:L register. In TPM v2, if only one byte of the TPMxCnVH:L registers was read
before the BDM mode became active, then any read of TPMxCnVH:L registers during BDM
mode returns the latched value of TPMxCNTH:L from the read buffer instead of the value in
the TPMxCnVH:L registers.
— This read coherency mechanism is cleared in TPM v3 in BDM mode if there is a write to
TPMxCnSC. Instead, in this condition the TPM v2 does not clear this read coherency
mechanism.
4. Write to TPMxCnVH:L registers
— Input Capture Mode (Section 15.4.2.1, “Input Capture Mode)
In this mode the TPM v3 does not allow the writes to TPMxCnVH:L registers. Instead, the
TPM v2 allows these writes.
— Output Compare Mode (Section 15.4.2.2, “Output Compare Mode)
In this mode and if (CLKSB:CLKSA not = 0:0), the TPM v3 updates the TPMxCnVH:L
registers with the value of their write buffer at the next change of the TPM counter (end of the
prescaler counting) after the second byte is written. Instead, the TPM v2 always updates these
registers when their second byte is written.
The following procedure can be used in the TPM v3 to verify if the TPMxCnVH:L registers
were updated with the new value that was written to these registers (value in their write buffer).
...
write the new value to TPMxCnVH:L;
read TPMxCnVH and TPMxCnVL registers;
while (the read value of TPMxCnVH:L is different from the new value written to
TPMxCnVH:L)
begin
read again TPMxCnVH and TPMxCnVL;
end
...
In this point, the TPMxCnVH:L registers were updated, so the program can continue and, for
example, write to TPMxC0SC without cancelling the previous write to TPMxCnVH:L
registers.
— Edge-Aligned PWM (Section 15.4.2.3, “Edge-Aligned PWM Mode)
In this mode and if (CLKSB:CLKSA not = 00), the TPM v3 updates the TPMxCnVH:L
registers with the value of their write buffer after that the both bytes were written and when the
MC9S08DN60 Series Data Sheet, Rev 3
282
Freescale Semiconductor