Impulse ACB-104.ULTRA (3514) - Manual (Page 10)

© Sealevel Systems, Inc. - 8 - ACB-104.ULTRA User Manual
Status Signal LED Headers
The 3514 has a pair of 2mm two-pin right angle headers at board location P6 (Tx
header) and P7 (Rx header) for connecting standard off-board LEDs (headers are
Hirose item# DF3-2P-2DS). Pin 1 is +5V (anode) through a 330
Ω resistor and can
be recognized by a square solder pad on the side of the board opposite the header.
Pin 2 is the LED control (cathode), which is driven by 5V CMOS logic (74HC123)
and has a round solder pad on the reverse side of the board.
An LED connected to the header can be used to monitor the activity status of
synchronous serial communications between the Z16C32 controller and the on-
board memory buffer. Using SeaMAC V4, both LEDs will flash when the Z16C32
controller is reading from or writing to the memory buffer (operates similar to the
activity LED on an Ethernet LAN card). This will confirm electrical continuity and
that the Z16C32 controller is communicating correctly. The LEDs will not flash for
sync characters or in cases where the Z16C32 controller is bypassed.
Programming For The LED Headers
Logic on the 3514 monitors local bus (DMA) ownership of the Z16C32 controller
and how the on-board memory (256K byte buffer) is accessed. The LED logic treats
the on-board buffer as 16 blocks of 16K bytes. The logic assumes that block zero
will be used for control data and upper memory reserved for actual data. If the
Z16C32 controller reads from memory block one through 15, the Tx LED (P6) will
flash at a preset rate. If the Z16C32 controller writes to memory block one through
15, the Rx LED (P7) will flash at a preset rate. The LED headers are tied to the
Z16C32 controller and will not flash if the controller is bypassed.
Storing the DMA control information in block zero of the on-board buffer, the LEDs
will flash only when actual data is being read from or written to upper buffer
memory. The LEDs ignore reads and writes to memory block zero and will not
flash. Also, the LEDS will not flash on sync characters since they are not stored in
memory. The control and status registers are defined below.