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MC68331CFC16 参数 Datasheet PDF下载

MC68331CFC16图片预览
型号: MC68331CFC16
PDF下载: 下载PDF文件 查看货源
内容描述: 用户手册 [User’s Manual]
分类和应用: 微控制器和处理器外围集成电路时钟
文件页数/大小: 254 页 / 1319 K
品牌: MOTOROLA [ MOTOROLA ]
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SYNCR Y field determines the count modulus for a modulo 64 down counter, causing  
it to divide by a value of Y + 1. When W or Y values change, VCO frequency changes,  
and there is a VCO relock delay. The SYNCR X bit controls a divide-by-two circuit that  
is not in the synthesizer feedback loop. When X = 0 (reset state), the divider is en-  
abled, and system clock frequency is one-fourth VCO frequency; setting X disables  
the divider, doubling clock speed without changing VCO speed. There is no relock de-  
lay when clock speed is changed by the X bit.  
Clock frequency is determined by SYNCR bit settings as follows:  
FSYSTEM = FREFERENCE[4(Y + 1)(22W + X)]  
The reset state of SYNCR ($3F00) produces a modulus-64 count.  
For the device to perform correctly, system clock and VCO frequencies selected by  
the W, X, and Y bits must be within the limits specified for the MCU. Do not use a com-  
bination of bit values that selects either an operating frequency or a VCO frequency  
greater than the maximum specified values in APPENDIX A ELECTRICAL CHARAC-  
TERISTICS.  
Table 4-7 shows clock control multipliers for all possible combinations of SYNCR bits.  
Table 4-8 shows clock frequencies available with a 32.768-kHz reference and a max-  
imum specified clock frequency of 20.97 MHz.  
4
Table 4-7 Clock Control Multipliers  
To obtain clock frequency in kilohertz, find counter modulus in the left column, then multiply reference frequency by value  
in appropriate prescaler cell.  
Modulus  
Y
Prescalers  
[W:X] = 00  
[W:X] = 01  
8
[W:X] = 10  
16  
[W:X] = 11  
32  
000000  
000001  
000010  
011111  
000011  
000100  
000101  
000110  
000111  
001000  
001001  
001010  
001011  
001100  
001101  
001110  
001111  
010000  
010001  
010010  
010011  
4
8
16  
32  
64  
12  
16  
20  
24  
28  
32  
36  
40  
44  
48  
52  
56  
60  
64  
68  
72  
76  
80  
84  
24  
48  
96  
32  
64  
128  
160  
192  
224  
256  
288  
320  
352  
384  
416  
448  
480  
512  
544  
576  
608  
640  
672  
40  
80  
48  
96  
56  
112  
128  
144  
160  
176  
192  
208  
224  
240  
256  
272  
288  
304  
320  
336  
64  
72  
80  
88  
96  
104  
112  
120  
128  
136  
144  
152  
160  
168  
MOTOROLA  
4-12  
SYSTEM INTEGRATION MODULE  
MC68331  
USER’S MANUAL