Datasheet

Chapter 16 Timer/PWM Module (S08TPMV3)
MC9S08SH8 MCU Series Data Sheet, Rev. 3
244 Freescale Semiconductor
The TPM channels are programmable independently as input capture, output compare, or edge-aligned
PWM channels. Alternately, the TPM can be configured to produce CPWM outputs on all channels. When
the TPM is configured for CPWMs, the counter operates as an up/down counter; input capture, output
compare, and EPWM functions are not practical.
If a channel is configured as input capture, an internal pullup device may be enabled for that channel. The
details of how a module interacts with pin controls depends upon the chip implementation because the I/O
pins and associated general purpose I/O controls are not part of the module. Refer to the discussion of the
I/O port logic in a full-chip specification.
Because center-aligned PWMs are usually used to drive 3-phase AC-induction motors and brushless DC
motors, they are typically used in sets of three or six channels.
16.2 Signal Description
Table 16-2 shows the user-accessible signals for the TPM. The number of channels may be varied from
one to eight. When an external clock is included, it can be shared with the same pin as any TPM channel;
however, it could be connected to a separate input pin. Refer to the I/O pin descriptions in full-chip
specification for the specific chip implementation.
Refer to documentation for the full-chip for details about reset states, port connections, and whether there
is any pullup device on these pins.
TPM channel pins can be associated with general purpose I/O pins and have passive pullup devices which
can be enabled with a control bit when the TPM or general purpose I/O controls have configured the
associated pin as an input. When no TPM function is enabled to use a corresponding pin, the pin reverts
to being controlled by general purpose I/O controls, including the port-data and data-direction registers.
Immediately after reset, no TPM functions are enabled, so all associated pins revert to general purpose I/O
control.
16.2.1 Detailed Signal Descriptions
This section describes each user-accessible pin signal in detail. Although Table 16-2 grouped all channel
pins together, any TPM pin can be shared with the external clock source signal. Since I/O pin logic is not
part of the TPM, refer to full-chip documentation for a specific derivative for more details about the
interaction of TPM pin functions and general purpose I/O controls including port data, data direction, and
pullup controls.
Table 16-2. Signal Properties
Name Function
EXTCLK
1
1
When preset, this signal can share any channel pin; however depending upon full-chip
implementation, this signal could be connected to a separate external pin.
External clock source which may be selected to drive the TPM counter.
TPMxCHn
2
2
n=channel number (1 to 8)
I/O pin associated with TPM channel n