MOTOROLA
12-2
CONFIGURABLE TIMER MODULE 7
MC68HC16R1/916R1
USER’S MANUAL
The time base buses originate in a counter submodule and are used by the action
submodules. Two time base buses are accessible to each submodule.
The bus interface unit submodule (BIUSM) allows all the CTM7 submodules to pass
data to and from the IMB via the submodule bus (SMB).
The counter prescaler submodule (CPSM) generates six different clock frequencies
which can be used by any counter submodule. This submodule is contained within the
BIUSM.
The free-running counter submodule (FCSM) has a 16-bit up counter with an
associated clock source selector, selectable time-base bus drivers, writable control
registers, readable status bits, and interrupt logic.The CTM7 has one FCSM.
The modulus counter submodule (MCSM) is an enhanced FCSM. A modulus register
gives the additional flexibility of recycling the counter at a count other than 64K clock
cycles. The CTM7 has one MCSM.
The single action submodule (SASM) provides an input capture and an output com-
pare for each of two bidirectional pins. A total of six SASMs (eight channels) are con-
tained in the CTM7.
The double-action submodule (DASM) provides two 16-bit input capture or two 16-bit
output compare functions that can occur automatically without software intervention.
The CTM7 has two DASMs.
The pulse width modulation submodule (PWMSM) can generate pulse width modulat-
ed signals over a wide range of frequencies, independently of other CTM output sig-
nals. PWMSMs are not affected by time base bus activity. The CTM7 has two
PWMSMs.
12.2 Address Map
The CTM7 address map occupies 256 bytes from address $YFF900 to $YFF9FF. All
CTM7 registers are accessible only when the CPU16 is in supervisor mode. All re-
served addresses return zero when read, and writes have no effect. Refer to
D.7 Con-
figurable Timer Module 7
for information concerning CTM7 address map and
register bit/field descriptions.
12.3 Time Base Bus System
The CTM7 time base bus system is composed of two 16-bit buses: TBB1 and TBB2.
These buses are used to transfer timing information from the counter submodules to
the action submodules. Two time base buses are available to each submodule. A
counter submodule can drive one of the two time base buses to which it is connected.
Each action submodule can choose one of the two time base buses to which it is con-
nected as its time base. Control bits within each CTM7 submodule select connection
to the appropriate time base bus.