VersaLogic STD32 VL-1225, Справочное руководство

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VL-1225/6 Analog Input/Output Board
4-3
Input Data Low Register
Input Data Low Register (IDLOW) — FF0CH
7 6 5 4 3 2 1 0
AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0
Figure 4-4. Input Data Low Register
The Input Data Low register is a read register containing the lower 8 bits of data from the A/D conversion
results. It is used in conjunction with the Input Data High register to read the complete 10- or 11-bit A/
D data word.
The Input Data Low register should always be read after reading the Input Data High register, never first.
See the Analog Input Operation section on page 5-1 for further information on accessing this register.
AD7-AD0 — A/D Data (Least Significant Bits).
These bits contain data bits D7 through D0 of the A/D
conversion results. See the Input Data Representation section for a discussion of input data formats.
Input Data High Register
Input Data High Register (IDHIGH) — FF0DH
7 6 5 4 3 2 1 0
BUSY X X X X AD10 AD9 AD8
Figure 4-3. Input Data High Register
The Input Data High register is a read register containing the conversion busy bit and the upper order
bits of data from the A/D conversion results. It is used in conjunction with the Input Data Low register
to read the complete 10- or 11-bit A/D data word.
The Input Data High register should always be read before reading the Input Data Low register.
See the Analog Input Operation section on page 5-1 for further information on accessing this register.
BUSY — Busy.
This bit is set to “1” when an A/D conversion is currently in progress, and automatically
resets to “0” when the A/D conversion is complete. Use this bit to determine when the analog input data
is valid.
X — Not Used.
These bits have no function in the VL-1225/6. They will read randomly as 1 or 0, therefore
it is important to mask these bits off when interpreting the A/D results.
AD10-AD8 — A/D Data (Most Significant Bits).
These bits contain data bits D10 through D8 of the A/D
conversion results. In 10-bit mode, AD10 has no function, and it will always = 0. See the Input Data
Representation section below for a discussion of input data formats.
Registers – Analog Input Registers