Modem SPI Register Descriptions
MC1321x Reference Manual, Rev. 1.6
5-24
Freescale Semiconductor
5.24
Tmr_Cmp3_B - Register 20
The Tmr_CMP3_B Register 20 stores the least significant 16 bits of the 24-bit compare value. Writing to
Register 20 causes an internal load of the full 24-bit comparator value (see
) and activates the mode presently set into the tmr_cmp3_dis control bit.
5.25
Tmr_Cmp4_A -Register 21
The Tmr_Cmp4_A Register 21 contains the disable bit for Timer Comparator 4 and stores the most
significant 8 bits of the 24-bit compare value (the lower 16 bits of the compare value are stored in
Tmr_CMP4_B Register 22). With regard to using the timer comparator:
•
It is suggested that the timer be disabled (writing
tmr_cmp4_dis to 1)
during system initialization
as the default mode out of reset is timer enabled
•
The value in Register 21 will not be loaded in the comparator and the affect of the timer disable bit
will not active until Register 22 is written. The 24-bit comparator value must be loaded into the
comparator register in parallel, and as a result, the load is caused by a write Register 22
Writing of Registers 21 and 22 can be done as a recursive SPI register write transaction or two separate
singular transactions. Writing to Register 22 as a separate operation will always use the present value of
Register 21 to load the comparator value and set the state of the disable bit.
Table 5-24. Register 1F Description
Name
Description
Operation
Bits 14-8
Reserved
Leave default
Bit 15
tmr_cmp3_dis
— This bit disables the Event Timer Comparator 3
interrupt and status bit.
1 = Disables Event Timer Compare 3
function.
0 = Enables Event Timer Compare 3
function (default).
Bits 7-0
tmr_cmp3[23:16]
— These bits represent the 8 most significant bits of
24-bit Event Timer 3 absolute time compare value, tmr_cmp3[23:0].
Default is 0xFF.
Register 20
0x20
BIT
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
tmr_cmp3[15:0]
TYPE
r/w
RESET
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0xFFFF
Table 5-25. Register 20 Description
Name
Description
Operation
Bits 15-0
tmr_cmp3[15:0]
— These bits represent the 16 least significant bits of 24-bit
Event Timer 3 absolute time compare value, tmr_cmp3[23:0].
Default is 0xFFFF.
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