Interfacing the MAX195 ADC to
abstract: application note for interfacing the max195 and max194 analog-to-digital converters (adcs) to the tms320c3x evaluation module. example demo code is given. the demo software configures the tms320c30 so that fsr1 and dr1 are inputs and clkr1 and xf1 are outputs. to read the max194/max195, the software briefly drives the xf1 output low. the demo software polls the serial receiver until a complete frame has been received. because this is just an interface demo, the software simply writes the received data word to the evm host data port.
overviewthe max195 16-bit adc can be interfaced to texas instruments' tms320c30 dsp by means of its serial interface. the interface uses four wires plus ground. this application note explains how to interface the max194/max195 evaluation kit to the tms320c3x evaluation module.
the example program was assembled using the tms320c3x/4x coff assembler version 4.50 and the tms320c3x/4f coff linker version 4.50 (copyright 1987 through 1992 by texas instruments incorporated).
interfacing the max194/max195 evkit to the tms320c3x evmmaxim's max194/max195 evaluation kit can be interfaced to texas instruments' tms320c3x evaluation module as follows: set the max194/max195 evkit jumpers according to table 1. solder a 2-x-5-pin berg strip into max194/max195 evkit area j3. the pc board is already wired as shown in table 2. connect a +5v power supply to the max194/max195 evkit. connect a 10-pin ribbon cable between the tms320c3x evm and the max194/max195 evkit. run the demo software. table 1. jumper settings jumper position function
ju1 closed connects the max195 sclk to ground
ju3 ext tms320 clkr1 drives the max195 conversion clock.
ju4 cs = gnd connects the max195 active-low cs to ground
ju5 qspi tms320 xf1 drives the max195 conv.
ju6 open max195 reset/calibration command
ju7 uni or open selects unipolar or bipolar transfer function
table 2. ribbon-cable signals
pin max195 tms320 pin max195 tms320
1 dgnd gnd 2 active-low eoc fsr1
3 not used 4 dout dr1
5 not used 6 not used
7 not used 8 active-low conv xf1
9 conclk clkr1 10 dgnd gnd
how it worksthe demo software (see the program-code listing that follows) configures the tms320c30 so that fsr1 and dr1 are inputs and clkr1 and xf1 are outputs. the software uses the xf1 output to initiate a conversion. the xf1 pulse drives the max194/max195 conversion start input. the clkr1 output provides the conversion clock to the max194/max195. data output from the max194/max195 is received on the dr1 input. the fsr1 frame start signal is driven by the max194/max195 eoc (end of conversion) signal, which marks the beginning of the serial frame.
to read the max194/max195, the software briefly drives the xf1 output low. the demo software polls the serial receiver until a complete frame has been received. because this is just an interface demo, the software simply writes the received data word to the evm host data port. tms320c3x/4x coff assembler, version 4.50 copyright (c) 1987-1992, texas instruments incorporated tms320c30 serial port initialization
project: max195 evkit interface to tms320c3x evm
project file = max195i
filename = max195i.asm
command file = max195i.cmd
compile with the following commands:
asm30 max195i -l
lnk30 max195i.cmd
pin assignments:
note: jumper ju8 must be open
and cs must be tied to gnd
timing diagram:
fastest clock 1mhz = (1 / 1000 nsec)
minimum receiver timer period = 4h
receive timer period = 4 = 0.9375mhz
(system clock frequency = 30mhz)
word diagram:
.sect vectors reset .word init int0 .word init int1 .word init int2 .word init int3 .word init xint0 .word init rint0 .word init xint1 .word init rint1 .word init tint0 .word init tint1 .word init dint .word init .data stck .word 0809f00h ; initial stack pointer ctrl .word 0808000h ; peripheral interface base address host_data .word 0804000h ; host data port address iof_amask .set 0000eh ; clear all xf1 bits in iof register iof_set_xf1 .set 00060h ; make xf1 pin an output; value = 1 iof_reset_xf1 .set 00020h ; make xf1 pin an output; value = 0 iof_input_xf1 .set 00080h ; make xf1 pin an input; read its value fs_amask .set 0f0ffh ; mask for an fs pin set_fs .set 00600h ; make fs a high output reset_fs .set 00200h ; make fs a low output get_fs .set 00800h ; input mask for fs pin d_amask .set 0ff0fh ; mask for a data pin set_d .set 00060h ; make d a high output reset_d .set 00020h ; make d a low output get_d .set 00080h ; input mask for d pin clk_amask .set 0fff0h ; mask for a clk pin set_clk .set 00006h ; make clk a high output reset_clk .set 00002h ; make clk a low output get_clk .set 00008h ; input mask for clk pin serial port global control register serglob1 .word 08100280h 08000000h: rreset - reset / enable the receiver 0080h: rclksrce - use internal receive clock (clkr pin is an output) 0200h: rvaren - receiver variable data rate 00100000h: rlen = 2 bytes (16 bits) pin assignment register for fsx, clkx, dx serprtx1 .word 00h assign clkx pin to general i/o make clkx an input assign dx pin to general i/o make dx an input assign fsx pin to general i/o make fsx an input pin assignment register for fsr, clkr, dr serprtr1 .word 0111h 0001h: assign clkr pin to serial port clock 0010h: assign dr pin to serial port receive data 0100h: assign fsr pin to serial port frame start serial port timer global control register sertim1 .word 03c0h xhld 0=hold transmit timer xc/p 0=pulse mode xclksrc 0=clkx pin increments the counter 0040h: rgo=1 -- start the receive timer 0080h: rhld 1=run receive timer 0100h: rc/p 1=clock (50% duty cycle) 0200h: rclksrc 1=use 7.5mhz time base (30mhz system clock/4) serial port timer period register sertim1val .word 040000h 0 h: transmit counter period 4 h: receive counter period receive timer period = 4 = 0.9375mhz .text init ldi 0,st ; initialize status register ldi 0,dp ; point data page pointer into rom ldi @stck,sp ; initialize stack pointer ; start with xf1 high ; ldi iof,r1 ; get xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_set_xf1,r1 ; make xf1 output a high value ldi r1,iof ; write new xf1 settings ; initialize serial port ; ldi @ctrl,ar0 ; peripheral interface address ldi @host_data,ar1 ; host interface address ldi @sertim1val,r0 sti r0,*+ar0(86) ; serial ch1 timer period ldi @serglob1,r0 sti r0,*+ar0(80) ; serial global register ldi @serprtx1,r0 sti r0,*+ar0(82) ; serial transmit control register ldi @serprtr1,r0 sti r0,*+ar0(83) ; serial receive control register ldi @sertim1,r0 sti r0,*+ar0(84) ; serial ch1 timer register xf1 signal is named active-low conv to max195 evkit this is how we set xf1: ldi iof,r1 ; get xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_set_xf1,r1 ; make xf1 output a high value ldi r1,iof ; write new xf1 settings this is how we clear xf1: ldi iof,r1 ; get xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_reset_xf1,r1 ; make xf1 output a low value ldi r1,iof ; write new xf1 settings next_sample: generate conversion start pulse ldi iof,r1 ; get xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_reset_xf1,r1 ; make xf1 output a low value ldi r1,iof ; write new xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_set_xf1,r1 ; make xf1 output a high value ldi r1,iof ; write new xf1 settings wait until serial receive is complete loop ldi *+ar0(80),r2 ; read global control register and 01h,r2 ; test the receiver ready bit bz loop ; loop until data is received get the received data ldi *+ar0(92),r3 ; copy received data into r3 this demo application does no processing -- it just makes the value available to the tms320c3x evm's host. sti r3,*+ar1(0) ; send r3 to host ldi 100,r0 ; delay wait_loop: subi 1,r0 bnz wait_loop br @next_sample ; this program runs forever .end
figure 1. schematic.
figure 2. timing
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overviewthe max195 16-bit adc can be interfaced to texas instruments' tms320c30 dsp by means of its serial interface. the interface uses four wires plus ground. this application note explains how to interface the max194/max195 evaluation kit to the tms320c3x evaluation module.
the example program was assembled using the tms320c3x/4x coff assembler version 4.50 and the tms320c3x/4f coff linker version 4.50 (copyright 1987 through 1992 by texas instruments incorporated).
interfacing the max194/max195 evkit to the tms320c3x evmmaxim's max194/max195 evaluation kit can be interfaced to texas instruments' tms320c3x evaluation module as follows: set the max194/max195 evkit jumpers according to table 1. solder a 2-x-5-pin berg strip into max194/max195 evkit area j3. the pc board is already wired as shown in table 2. connect a +5v power supply to the max194/max195 evkit. connect a 10-pin ribbon cable between the tms320c3x evm and the max194/max195 evkit. run the demo software. table 1. jumper settings jumper position function
ju1 closed connects the max195 sclk to ground
ju3 ext tms320 clkr1 drives the max195 conversion clock.
ju4 cs = gnd connects the max195 active-low cs to ground
ju5 qspi tms320 xf1 drives the max195 conv.
ju6 open max195 reset/calibration command
ju7 uni or open selects unipolar or bipolar transfer function
table 2. ribbon-cable signals
pin max195 tms320 pin max195 tms320
1 dgnd gnd 2 active-low eoc fsr1
3 not used 4 dout dr1
5 not used 6 not used
7 not used 8 active-low conv xf1
9 conclk clkr1 10 dgnd gnd
how it worksthe demo software (see the program-code listing that follows) configures the tms320c30 so that fsr1 and dr1 are inputs and clkr1 and xf1 are outputs. the software uses the xf1 output to initiate a conversion. the xf1 pulse drives the max194/max195 conversion start input. the clkr1 output provides the conversion clock to the max194/max195. data output from the max194/max195 is received on the dr1 input. the fsr1 frame start signal is driven by the max194/max195 eoc (end of conversion) signal, which marks the beginning of the serial frame.
to read the max194/max195, the software briefly drives the xf1 output low. the demo software polls the serial receiver until a complete frame has been received. because this is just an interface demo, the software simply writes the received data word to the evm host data port. tms320c3x/4x coff assembler, version 4.50 copyright (c) 1987-1992, texas instruments incorporated tms320c30 serial port initialization
project: max195 evkit interface to tms320c3x evm
project file = max195i
filename = max195i.asm
command file = max195i.cmd
compile with the following commands:
asm30 max195i -l
lnk30 max195i.cmd
pin assignments:
note: jumper ju8 must be open
and cs must be tied to gnd
timing diagram:
fastest clock 1mhz = (1 / 1000 nsec)
minimum receiver timer period = 4h
receive timer period = 4 = 0.9375mhz
(system clock frequency = 30mhz)
word diagram:
.sect vectors reset .word init int0 .word init int1 .word init int2 .word init int3 .word init xint0 .word init rint0 .word init xint1 .word init rint1 .word init tint0 .word init tint1 .word init dint .word init .data stck .word 0809f00h ; initial stack pointer ctrl .word 0808000h ; peripheral interface base address host_data .word 0804000h ; host data port address iof_amask .set 0000eh ; clear all xf1 bits in iof register iof_set_xf1 .set 00060h ; make xf1 pin an output; value = 1 iof_reset_xf1 .set 00020h ; make xf1 pin an output; value = 0 iof_input_xf1 .set 00080h ; make xf1 pin an input; read its value fs_amask .set 0f0ffh ; mask for an fs pin set_fs .set 00600h ; make fs a high output reset_fs .set 00200h ; make fs a low output get_fs .set 00800h ; input mask for fs pin d_amask .set 0ff0fh ; mask for a data pin set_d .set 00060h ; make d a high output reset_d .set 00020h ; make d a low output get_d .set 00080h ; input mask for d pin clk_amask .set 0fff0h ; mask for a clk pin set_clk .set 00006h ; make clk a high output reset_clk .set 00002h ; make clk a low output get_clk .set 00008h ; input mask for clk pin serial port global control register serglob1 .word 08100280h 08000000h: rreset - reset / enable the receiver 0080h: rclksrce - use internal receive clock (clkr pin is an output) 0200h: rvaren - receiver variable data rate 00100000h: rlen = 2 bytes (16 bits) pin assignment register for fsx, clkx, dx serprtx1 .word 00h assign clkx pin to general i/o make clkx an input assign dx pin to general i/o make dx an input assign fsx pin to general i/o make fsx an input pin assignment register for fsr, clkr, dr serprtr1 .word 0111h 0001h: assign clkr pin to serial port clock 0010h: assign dr pin to serial port receive data 0100h: assign fsr pin to serial port frame start serial port timer global control register sertim1 .word 03c0h xhld 0=hold transmit timer xc/p 0=pulse mode xclksrc 0=clkx pin increments the counter 0040h: rgo=1 -- start the receive timer 0080h: rhld 1=run receive timer 0100h: rc/p 1=clock (50% duty cycle) 0200h: rclksrc 1=use 7.5mhz time base (30mhz system clock/4) serial port timer period register sertim1val .word 040000h 0 h: transmit counter period 4 h: receive counter period receive timer period = 4 = 0.9375mhz .text init ldi 0,st ; initialize status register ldi 0,dp ; point data page pointer into rom ldi @stck,sp ; initialize stack pointer ; start with xf1 high ; ldi iof,r1 ; get xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_set_xf1,r1 ; make xf1 output a high value ldi r1,iof ; write new xf1 settings ; initialize serial port ; ldi @ctrl,ar0 ; peripheral interface address ldi @host_data,ar1 ; host interface address ldi @sertim1val,r0 sti r0,*+ar0(86) ; serial ch1 timer period ldi @serglob1,r0 sti r0,*+ar0(80) ; serial global register ldi @serprtx1,r0 sti r0,*+ar0(82) ; serial transmit control register ldi @serprtr1,r0 sti r0,*+ar0(83) ; serial receive control register ldi @sertim1,r0 sti r0,*+ar0(84) ; serial ch1 timer register xf1 signal is named active-low conv to max195 evkit this is how we set xf1: ldi iof,r1 ; get xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_set_xf1,r1 ; make xf1 output a high value ldi r1,iof ; write new xf1 settings this is how we clear xf1: ldi iof,r1 ; get xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_reset_xf1,r1 ; make xf1 output a low value ldi r1,iof ; write new xf1 settings next_sample: generate conversion start pulse ldi iof,r1 ; get xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_reset_xf1,r1 ; make xf1 output a low value ldi r1,iof ; write new xf1 settings and iof_amask,r1 ; don't touch xf0 settings or iof_set_xf1,r1 ; make xf1 output a high value ldi r1,iof ; write new xf1 settings wait until serial receive is complete loop ldi *+ar0(80),r2 ; read global control register and 01h,r2 ; test the receiver ready bit bz loop ; loop until data is received get the received data ldi *+ar0(92),r3 ; copy received data into r3 this demo application does no processing -- it just makes the value available to the tms320c3x evm's host. sti r3,*+ar1(0) ; send r3 to host ldi 100,r0 ; delay wait_loop: subi 1,r0 bnz wait_loop br @next_sample ; this program runs forever .end
figure 1. schematic.
figure 2. timing
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