Rainbow Electronics MAX188 - Manual (Page 23)

MAX186/MAX188
Low-Power, 8-Channel,
Serial 12-Bit ADCs
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TMS320C3x to MAX186 Interface
Figure 22 shows an application circuit to interface the
MAX186/MAX188 to the TMS320 in external clock
mode. The timing diagram for this interface circuit is
shown in Figure 23.
Use the following steps to initiate a conversion in the
MAX186/MAX188 and to read the results:
1) The TMS320 should be configured with CLKX (trans-
mit clock) as an active-high output clock and CLKR
(TMS320 receive clock) as an active-high input clock.
CLKX and CLKR of the TMS320 are tied together with
the SCLK input of the MAX186/MAX188.
2) The MAX186/MAX188 CS is driven low by the XF_
I/O port of the TMS320 to enable data to be clocked
into DIN of the MAX186/MAX188.
3) An 8-bit word (1XXXXX11) should be written to the
MAX186/MAX188 to initiate a conversion and place
the device into external clock mode. Refer to Table
2 to select the proper XXXXX bit values for your spe-
cific application.
4) The SSTRB output of the MAX186/MAX188 is moni-
tored via the FSR input of the TMS320. A falling
edge on the SSTRB output indicates that the conver-
sion is in progress and data is ready to be received
from the MAX186/MAX188.
XF
CLKX
CLKR
DX
DR
FSR
CS
SCLK
DIN
DOUT
SSTRB
TMS320C3x
MAX186
MAX188
Figure 22. MAX186/MAX188 to TMS320 Serial Interface
• • • •
• • • •
• • • •
• • • •
CS
SCLK
SSTRB
DIN
Figure 21. QSPI Assembly-Code Timing
5) The TMS320 reads in one data bit on each of the
next 16 rising edges of SCLK. These data bits rep-
resent the 12-bit conversion result followed by four
trailing bits, which should be ignored.
6) Pull CS high to disable the MAX186/MAX188 until
the next conversion is initiated.