VTI Instruments EX1000A, User Manual

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EX10xxA Function Calls 141
ViUInt32 limits_len; /* array size of limit data */
ViUInt32 *limits_val; /* limit data 4 bits for each channel */
} limits;
};
The data format of the limit values ( limits_val ) is as follows:
index 0: set 0 low limit exceeded, channels 0-31
index 1: set 0 low limit exceeded, channels 32-63
index 2: set 0 high limit exceeded, channels 0-31
index 3: set 0 high limit exceeded, channels 32-63
index 4: set 1 low limit exceeded, channels 0-31
index 5: set 1 low limit exceeded, channels 32-63
index 6: set 1 high limit exceeded, channels 0-31
index 7: set 1 high limit exceeded, channels 32-63
Each bit is “1” if the limit was exceeded and “0” if it was not. Channels 48 through 63 are CJC and special channels
which can be ignored by most users.
The ticks value (
ticks_val ) data format is a tightly packed array of unsigned bytes. This is used rather than 16-bit
integers as this is the most efficient way for the RPC to package the data. As a result, the length of the data is
actually twice the channel count and must be manipulated as follows in order to read the data:
uint16_t real_ticks_ch0 = ntohs(datapage.x_ticks.x_ticks_val[0] << 8 | datapage.x_ticks.x_ticks_val[1]);
uint16_t real_ticks_ch1 = ntohs(datapage.x_ticks.x_ticks_val[2] << 8 | datapage.x_ticks.x_ticks_val[3]);
or, alternatively:
uint16_t real_ticks_ch0 = ntohs(*((uint16_t*)&datapage.x_ticks.x_ticks_val[0]));
uint16_t real_ticks_ch1 = ntohs(*((uint16_t*)&datapage.x_ticks.x_ticks_val[2]));
E
XAMPLE
See Retrieving Data (Read FIFO and Streaming Data) in Section 5 for an example.