MOTOROLA
MC68CK338
78
MC68CK338TS/D
6 Configurable Timer Module 6
The configurable timer module 6 (CTM6) belongs to a family of timer modules for the Motorola Modular
Microcontroller Family. The timer architecture is modular relative to the number of time bases (counter
submodules) and channels (action submodules or timer I/O pins) that are included.
The CTM6 consists of several submodules which are located on either side of the CTM6 internal sub-
module bus (SMB). All data and control signals within the CTM6 are passed over this bus. The SMB is
connected to the outside world via the bus interface unit submodule (BIUSM), which is connected to the
intermodule bus (IMB), and subsequently the CPU. This configuration allows the CPU to access the
data and control registers in each CTM6 submodule on the SMB. Four local time base buses TBB[1:4],
each 16-bits wide, are used to transfer timing information from counters to action submodules. Each
CTM6 submodule can be connected to two TBBs. Figure 17 shows a block diagram of the CTM6.
6.1 Overview
The time base bus system connects the four counter submodules to the eleven double-action submod-
ules (DASMs) and eight single-action submodules (SASM) channels.
The bus interface unit submodule (BIUSM) allows all the CTM6 submodules to communicate to 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, software writable control registers, software readable status
bits, and interrupt logic. One FCSM is contained in the CTM6.
The modulus counter submodule (MCSM) is an enhancement of the FCSM. A modulus register gives
the additional flexibility of recycling the counter at a count other than 64K clock cycles. Three MCSMs
are contained in the CTM6.
The single action submodule (SASM) provides an input capture and an output compare for each of two
bidirectional pins. A total of four SASMs (eight channels) are contained in the CTM6.
The double-action submodule (DASM) provides two 16-bit input captures or two 16-bit output compare
functions that can occur automatically without software intervention. Eleven DASMs are contained in
the CTM6.
The real-time clock submodule (RTCSM) provides a real time clock function independent of other CTM6
submodules. This time counter is driven by a dedicated low frequency oscillator (32.768 kHz) for low
power consumption.
A parallel port I/O submodule (PIOSM) handles up to eight input/output pins. Each pin of the PIOSM
may be programmed as an input or an output under software control. One PIOSM is contained in the
CTM6.
The static RAM submodule (RAMSM) provides 32 bytes (16 words) of contiguous memory locations
and takes the address space of four standard submodules. The RAMSM works as a stand-by memory.
Two RAMSMs are contained in the CTM6.
The standby power switch changes the power source of the RTCSM prescaler, counters, and oscillator,
as well as the two RAMSMs to VRTC when VDD drops below its minimum specified value.
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Freescale Semiconductor, Inc.
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