
MOTOROLA
2-2
CTM
REFERENCE
BUS INTERFACE UNIT SUBMODULE (BIUSM)
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2
2.4
STOP and WAIT action on the BIUSM
When the STOP instruction on CPU32 or the WAIT instruction on CPU16 is executed, only the
CPU is stopped; the CTM continues to operate as normal. (To stop the CTM operation selectively,
refer to the description of the STOP bit in Section 2.5.1).
2.5
BIUSM registers
The BIUSM register map comprises four 16-bit register locations. As shown in Table 2-1, the register
block contains the three BIUSM registers and one reserved register. The BIUSM register block
always occupies the first four register locations in the CTM register space and cannot be relocated
within the CTM structure. All unused bits and reserved address locations return zero when read by
the software. Writing to unused bits and reserved address locations has no effect.
Note:
All BIUSM register addresses in this section are specified as offsets from the base
address of the CTM.
2.5.1
BIUMCR — BIUSM module configuration register
The BIUMCR register contains nine defined bits that allow the software to control five functions of
the CTM: enabling/disabling of the module, response to FREEZE, vector base address, interrupt
arbitration number and access to the time base buses (via the time base register).
(1) Offset fromthe base address of the CTM.
(1) Offset fromthe base address of the CTM.
Table 2-1
BIUSM register map
Address
(1)
$00
$02
$04
$06
15
8 7
0
BIUSMmodule configuration register (BIUMCR)
BIUSMtest register (BIUTEST)
BIUSMtime base register (BIUTBR)
Bit:
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
BIUMCR
$00
(1)
STOP
FRZ
VECT7VECT6 IARB2 IARB1 IARB0
TBRS1
TBRS0
Reset:
0
0
0
1
1
0
0
0
0
0
0
0
0
0
0
0
F
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