MPC555
/
MPC556
MODULAR INPUT/OUTPUT SUBSYSTEM (MIOS1)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
15-16
15.10.1.1 MMCSM Up-Counter Register (MMCSMCNT)
The MMCSMCNT register contains the 16-bit value of the up counter. Note that writing
to MMCSMCNT simultaneously writes to MMCSMML.
U = Unaffected by reset
15.10.1.2 MMCSM Modulus Latch Register (MMCSMML)
The MMCSMML is a read/write register containing the 16-bit value of the up-counter.
U = Unaffected by reset
15.10.1.3 MMCSM Status/Control Register (Duplicated)
The MMCSMSCRD and the MMCSMSCR are the same registers accessed at two dif-
ferent addresses. Reading or writing to one of these two addresses has exactly the
same effect.
NOTE
The user should not write directly to the address of the MMCSM-
SCRD. This register’s address may be reserved for future use and
should not be accessed by the software to assure future software
compatibility.
MMCSMCNT
— MMCSM Up-Counter Register
0x30 6030
0x30 60B0
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSB
15
CNT
RESET:
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
Table 15-12 MMCSMCNT Bit Descriptions
Bit(s)
Name
Description
0:15
CNT
Counter value. These read/write data bits represent the 16-bit value of the up-counter. CNT con-
tains the value that is driven onto the 16-bit counter bus.
MMCSMML
— MMCSM Modulus Latch Register
0x30 6032
0x30 60B2
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSB
15
ML
RESET:
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
Table 15-13 MMCSMML Bit Descriptions
Bit(s)
Name
Description
0:15
ML
Modulus latches. These bits are read/write data bits containing the 16-bit modulus value to be
loaded into the up-counter.
The value loaded in this register must be the two’s complement of the desired modulus count.
The up-counter increments from this two’s complement value up to 0xFFFF to get the correct
number of steps before an overflow is generated to reload the modulus value into the up-
counter. A value of 0x0000 should be used for a free-running counter.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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