23-Jul-2011
ref: www.mail-archive.com/time-nuts@febo.com/msg39720.html

Setup using a modern microcontroller (32-bit ARM @ 48MHz) to drive the 5370's device bus. The original 5370 CPU card uses an 8-bit Motorola m6800 running @ 1.5MHz. Atmel AT91SAM7X micro evaluation-kit board on left drives the bus via ribbon cable. Cables on left edge of board connect to host development computer. Bottom right ribbon carries HPIB card signals back to logic analyzer.
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SAM7X evaluation-kit board. Top connectors: JTAG, USB, 10/100 Ethernet, serial x 2. Two 31-bit GPIO ports appear on header pins at left (connected here to ribbon). SAM7X is the 100-pin TQFP, 48-pin Ethernet PHY above. A replacement board for the 5370 would have fewer components than this board.
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Front panel measurement function timings, original instrument versus emulated firmware.

Logic analyzer trace of binary TI data transfer to host via Ethernet connection. The green cursors measure the time to send one packet containing 512 measurements. So 512 * 164Hz = 84K meas/sec. The waveforms on the left where the 5370 device bus LA01/RW lines are madly flapping is where the count chain regs are read. The quiet portion in the center-right is the network stack running (entirely on the micro, so no 5370 bus cycles involved). "Run" is the software-controlled signal triggered on.

Screen shot of host computer. The left window is the serial debug output from the emulator & micro. The middle is the fast C code loop that reads the count chain regs (4 writes, 6 reads) and performs the conversion from 5 to 2-bytes. On the right are the reconstructed TI values on the host (from the 10 MHz internal reference looped back to the Start input, so 100 ns +/-). Click image for larger.