Datasheet

Chapter 16 Timer/PWM Module (S08TPMV3)
MC9S08SH8 MCU Series Data Sheet, Rev. 3
248 Freescale Semiconductor
16.3 Register Definitio
This section consists of register descriptions in address order. A typical MCU system may contain multiple
TPMs, and each TPM may have one to eight channels, so register names include placeholder characters to
identify which TPM and which channel is being referenced. For example, TPMxCnSC refers to timer
(TPM) x, channel n. TPM1C2SC would be the status and control register for channel 2 of timer 1.
16.3.1 TPM Status and Control Register (TPMxSC)
TPMxSC contains the overflow status flag and control bits used to configure the interrupt enable, TPM
configuration, clock source, and prescale factor. These controls relate to all channels within this timer
module.
76543210
RTOF
TOIE CPWMS CLKSB CLKSA PS2 PS1 PS0
W0
Reset 00000000
Figure 16-7. TPM Status and Control Register (TPMxSC)
Table 16-3. TPMxSC Field Descriptions
Field Description
7
TOF
Timer overflow flag. This read/write flag is set when the TPM counter resets to 0x0000 after reaching the modulo
value programmed in the TPM counter modulo registers. Clear TOF by reading the TPM status and control
register when TOF is set and then writing a logic 0 to TOF. If another TPM overflow occurs before the clearing
sequence is complete, the sequence is reset so TOF would remain set after the clear sequence was completed
for the earlier TOF. This is done so a TOF interrupt request cannot be lost during the clearing sequence for a
previous TOF. Reset clears TOF. Writing a logic 1 to TOF has no effect.
0 TPM counter has not reached modulo value or overflow
1 TPM counter has overflowed
6
TOIE
Timer overflow interrupt enable. This read/write bit enables TPM overflow interrupts. If TOIE is set, an interrupt is
generated when TOF equals one. Reset clears TOIE.
0 TOF interrupts inhibited (use for software polling)
1 TOF interrupts enabled
5
CPWMS
Center-aligned PWM select. When present, this read/write bit selects CPWM operating mode. By default, the
TPM operates in up-counting mode for input capture, output compare, and edge-aligned PWM functions. Setting
CPWMS reconfigures the TPM to operate in up/down counting mode for CPWM functions. Reset clears CPWMS.
0 All channels operate as input capture, output compare, or edge-aligned PWM mode as selected by the
MSnB:MSnA control bits in each channel’s status and control register.
1 All channels operate in center-aligned PWM mode.