Reference Manual
Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 198
I6803/I6853/I6903/I6953 MACRO IC Hardware Clock Control
Range: 0 - 4095
Units: Individual Clock Dividers
I6803 = Encoder SCLK Divider
+ 8 * PFM_CLK Divider
+ 64 * DAC_CLK Divider
+ 512 * ADC_CLK Divider
where:
Encoder SCLK Frequency = 39.3216 MHz / (2 ^ Encoder SCLK Divider)
PFM_CLK Frequency = 39.3216 MHz / (2 ^ PFM_CLK Divider)
DAC_CLK Frequency = 39.3216 MHz / (2 ^ DAC_CLK Divider)
ADC_CLK Frequency = 39.3216 MHz / (2 ^ ADC_CLK Divider)
Default: 2258 = 2 + (8 * 2) + (64 * 3) + (512 * 4)
Encoder SCLK Frequency = 39.3216 MHz / (2 ^ 2) = 9.8304 MHz
PFM_CLK Frequency = 39.3216 MHz / (2 ^ 2) = 9.8304 MHz
DAC_CLK Frequency = 39.3216 MHz / (2 ^ 3) = 4.9152 MHz
ADC_CLK Frequency = 39.3216 MHz / (2 ^ 4) = 2.4576 MHz
Note:
This I-variable is active only if the MACRO IC is present, and is a DSPGATE2 IC.
The presence and type of MACRO ICs are reported in I4902 and I4903.
I6803, I6853, I6903, and I6953 control the frequency of four hardware clock signals -- SCLK,
PFM_CLK, DAC_CLK, and ADC_CLK -- for the two supplemental machine interface channels of
MACRO ICs 0, 1, 2, and 3, respectively, provided they are DSPGATE2 ICs. These are 12-bit variables
consisting of four independent 3-bit controls, one for each of the clocks. Each of these clock frequencies
can be divided down from a starting 39.3216 MHz frequency by powers of 2, 2
N
, from 1 to 128 times
(N=0 to 7). This means that the possible frequency settings for each of these clocks are:
Frequency
Divide by
Divider N in 1/2
N
39.3216 MHz
1
0
19.6608 MHz
2
1
9.8304 MHz
4
2
4.9152 MHz
8
3
2.4576 MHz
16
4
1.2288 MHz
32
5
614.4 kHz
64
6
307.2 kHz
128
7
Very few Turbo PMAC2 users will be required to change the setting of these variables from their default
values.
Note:
In firmware versions V1.933 and older, bit m of I67 must be set to 1 in order to be
able to access this variable on MACRO IC m. In V1.934 and V1.935, Turbo
PMAC automatically enables this variable for any IC present at power-up/reset. In
V1.936 and newer, I2m must contain the base address of MACRO IC m in order to
access this variable on the IC.