MC68336/376
CONFIGURABLE TIMER MODULE 4
MOTOROLA
USER’S MANUAL
10-3
In the CTM4, TBB2 is global and accessible to every submodule. TBB1 and TBB4 are
split to form two local time base buses. Table 10-1 shows which time base buses are
available to each CTM4 submodule.
Each PWMSM has an independent 16-bit counter and 8-bit prescaler clocked by the
PCLK1 signal, which is generated by the CPSM. The PWMSMs are not connected to
10.4 Bus Interface Unit Submodule (BIUSM)
The BIUSM connects the SMB to the IMB and allows the CTM4 submodules to com-
municate with the CPU32. The BIUSM also communicates CTM4 submodule interrupt
requests to the IMB, and transfers the interrupt level, arbitration number and vector
number to the CPU32 during the interrupt acknowledge cycle.
10.4.1 STOP Effect On the BIUSM
When the CPU32 STOP instruction is executed, only the CPU32 is stopped; the CTM4
continues to operate as normal.
10.4.2 Freeze Effect On the BIUSM
CTM4 response to assertion of the IMB FREEZE signal is controlled by the FRZ bit in
the BIUSM configuration register (BIUMCR). Since the BIUSM propagates FREEZE
to the CTM4 submodules via the SMB, the setting of FRZ affects all CTM4 submod-
ules.
If the IMB FREEZE signal is asserted and FRZ = 1, all CTM4 submodules freeze. The
following conditions apply when the CTM4 is frozen:
All submodule registers can still be accessed.
The CPSM, FCSM, MCSM, and PWMSM counters stop counting.
The IN status bit still reflects the state of the FCSM external clock input pin.
The IN2 status bit still reflects the state of the MCSM external clock input pin, and
the IN1 status bit still reflects the state of the MCSM modulus load input pin.
DASM capture and compare functions are disabled.
The DASM IN status bit still reflects the state of its associated pin in the DIS,
IPWM, IPM, and IC modes. In the OCB, OCAB, and OPWM modes, IN reflects
the state of the DASM output flip flop.
When configured for OCB, OCAB, or OPWM modes, the state of the DASM
Table 10-1 CTM4 Time Base Bus Allocation
Global/Local Time Base
Bus Allocation
Global/Local Time Base
Bus Allocation
Submodule
Global Bus A
Global Bus B
Submodule
Global Bus A
Global Bus B
DASM9
TBB1
TBB2
MCSM 2
TBB4
TBB2
DASM10
TBB1
TBB2
DASM 3
TBB4
TBB2
MCSM 11
TBB1
TBB2
DASM 4
TBB4
TBB2
FCSM 12
TBB1
TBB2
336376UMBook Page 3 Friday, November 15, 1996 2:09 PM