Sundance SMT381 2004 - Manual (Page 42)

0x5 Reserved
0x6 Reserved
0x7 Reserved
0x8 Reserved
0x9 Reserved
0xA Reserved
0xB Reserved
0xC Reserved
0xD Reserved
0xE Reserved
0xF FPGA Reset
Figure 23. Packet Structure – Defined Commands.
5.2 Reading and Writing Registers
Control packets are sent to the SMT381-VP over ComPort 3. This is a bi-directional
interface and data can be sent to the SMT381-VP over ComPort 3 and also received
over it. ComPort 3 is used to write control information to the SMT381-VP. Data is
written by sending a ‘Write Packet’ (Command 0x1). Data is read by first writing a
‘Read Request’ (Command 0x2) packet containing the address to be read over
ComPort 3. The SMT381-VP will collect the required data and send a ‘Read Packet’
out over ComPort 3 containing the requested data. The format of a ‘Read Packet’ is
the same as that of a write packet. (For the example firmware ComPort 3 is the
designated communications port on the SMT381-VP. This ComPort may however be
connected to any ComPort on the Host.)
Host
Data LSB
SMT391-VP
ComPort 3
ComPort 3
Byte 0
Data MSB Byte 1
Address Byte 3
Address / Command Byte 4
1) Write Packet (0x1), Or Read Request Packet (0x2)
Data LSB Byte 0
Data MSB Byte 1
Address Byte 3
Address / Command Byte 4
2) Read Packet
Figure 24. Control Register Read Sequence.
Example 1:
Sending 0x1001FFFF over ComPort3 from the Host to the SMT381-VP will Write, to
Address 0x001, Data FFFF
Example 2: