User's Manual

UMAC Turbo CPU/Communications Board Hardware Manual
Upgrading Communications Firmware 31
The DPRAM offset is the number of bytes from the base DPRAM location. To compute this value, take
the UMAC Turbo CPU/Communications Board DPRAM address and multiply its offset by 4. The offset
is always the last three digits of the DPRAM address. For example, for the address $60D60 multiply
$D60 by 4 to compute the offset; the offset for UMAC Turbo CPU/Communications Board address
$60D60 is 0x3580. For X memory address, the same applies, except that 2 must be added to the offset
calculation.
It is not wise to call PmacDprGetMem for each item of data, due to the structure of USB. The reason is
that each call can take 1 msec, but so would a single call getting all the data. More efficient coding would
be as follows:
typedef struct {
DWORD dwData;
WORD wData1;
WORD wData2;
Float fData;
} Data;
PmacDprGetMem(0,0x3580,12,&Data);
Response to a request for 1KB of data with a PmacDprGetMem call would take ~1 msec; however, if
PmacDprGetMem was called for each byte, it would have taken ~1024msec.
Getting the Best Performance from USB
For the best possible performance when using USB communications, use a computer capable of USB 2.0.
To determine if the computer has USB 2.0:
1. Right click on the My Computer icon on the desktop.
2. Click on the Properties button from the drop down menu that appears.
3. Click the Hardware tab, followed by the Devine Manager button.
4. From the Device Manager dialog, select the + on Universal Serial bus Controllers. The phrase
Universal Host Controller or Open Host Controller will appear. In addition, there may be a phrase
Enhanced USB Host Controller. If Enhanced appears, the computer is capable of USB 2.0. If
Enhanced does not appear, the computer does not support it.
If the computer does not support USB 2.0, consider either a computer upgrade if USB communication
speed is important to the operation or purchase a USB 2.0 PCI expansion card available from any
local computer store.