
TS-7250 MANUAL
CONNECTORS AND HEADERS
values returned by the Cirrus A/D converter to voltage.
5.7 A/D Header - Optional MAX197
The
TS-7250
supports an optional eight-channel, 12-bit A/D converter (ADC) with a
conversion time of 12 uS. This will allow up to 60,000 samples per second. Each channel
is independently software programmable for a variety of analog input ranges: -10V to
+10V, -5V to +5V, 0V to +10V, or 0V to +5V. This allows an effective dynamic range of 14
bits.
Table: A/D Registers (MAX197)
I/O Address
Action
0x10F0_0000 Write
Initiate A/D Conversion
0x10F0_0000 Read LSB of Conversion
0x10F0_0001 Read MSB of Conversion
0x2240_0000 Read Bit 0 = 1 if A/D option installed
0x1080_0000 Read Bit 7 = 0 when Conversion completed
Each channel is overvoltage tolerant from -16V to + 16V, and a fault condition on any
channel will not affect the conversion result of the selected channel. This is all
accomplished with a 5V only power supply; no negative supply voltage is required. The
Maxim MAX197 chip can be replaced with a MAX199 chip if a lower range of analog input
levels is required (-4V to +4V, -2V to +2V, 0V to 4V, and 0V to 2V).
A/D Control Register (0x10F0_0000 Write)
Bit
Description
Details
0-2
Analog channel select Channels 0-7
3
Unipolar / Bipolar
0 = Unipolar (i.e. 0 to +5V)
1 = Bipolar (i.e. -5V to +5V)
4
Range select
0 = 5V range
1 = 10V range
5-7
Mode bits
Set to 0, 1, 0
A read at I/O location 0x2240_0000 bit 0 returns a "1" when the A/D option is installed on
the
TS-7250
.
Single Sample Acquisition Procedure
An acquisition is initiated by writing to I/O location 0x10F0_0000. The value written to this
location determines the channel to convert (bits 0-2) and selects one of four input ranges
(bits 3 and 4). Bits 5, 6, and 7 should be set to 0, 1, 0 respectively. After the write cycle to
location 0x10F0_0000, the MAX197 completes the A/D conversion in about 12 mS. Bit 7
at I/O location 0x2240_0000 may be polled to determine when the conversion is complete
(zero = complete). The conversion result is now available at locations 0x10F0_0000 (LSB)
and 0x10F0_0001 (MSB). A single word read at 0x10F0_0000 can also be used. When
using unipolar modes, the result is in binary format with the upper 4 bits of the MSB equal
to zero. When a bipolar mode is used, the result is in twos-complement binary with the
upper 4 bits (Bits 12-15) equal to bit 11 (sign extended).
Table: A/D Header Pin Out (MAX197)
GND GND GND GND GND GND GND
GND
2
4
6
8
10
12
14
16
1
3
5
7
9
11
13
15
ch0
ch1
ch2
ch3
ch4
ch5
ch6
ch7
If more details on the A/D converter specifications are required, go to the Maxim web site
and search for MAX197.
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