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5.4
Control by Link
The SMCS332SpW offers the possibility to be used in a so-called "remote mode" which means that for controlling the
SMCS332SpW (read/write registers) no local controller (µController, CPU, FPGA etc.) is required. Instead, the
SMCS332SpW is being configured and controlled using one of the three links as a dedicated control link. Since the HOCI is
no longer used to access the SMCS332SpW registers locally, it is instead available as a 32-bit bidirectional general purpose
I/O (GPIO) port. The direction (in/out) of each bit of this port can be programmed individually.
5.4.1
Selecting remote mode
The external signal "BOOTLINK" (pin 32) must be tied to "1". This will set the SMCS332SpW to remote mode. It is not
possible to switch the SMCS332SpW into remote mode by software.
5.4.2
Determination of the control link
After the reset signal is released the SMCS332SpW will wait for NULL characters on the three links. It will not start a link
until it has received NULL characters on this link. Only then the SMCS332SpW will send NULL characters itself. After the
links are active, the SMCS332SpW scans these links for data (characters). The link on which the SMCS332SpW receives
data first is then identified and determined as "control link". This means that each of the 3 SMCS332SpW links can function
as control link. Which of the links is used as control link is only determined by the first appearance of data on a link directly
after it is started. That link then operates as "control link" until the SMCS332SpW is reset by the reset signal RESET
5.4.3
Protocol and Commands
The protocol of the SMCS332SpW in remote mode provides two commands: Read and Write. A read command requires at
least one byte and a write command requires at least two bytes. Each command packet must be terminated by an EOP
character. Data received on the control link is interpreted according to this simple protocol. Bit 7 (the MSB) of the first byte
received on the control link determines whether the command is a Read (bit 7 = 1) or a Write (bit 7 = 0) command. All
internal registers of the SMCS332SpW can be written
Read Command:
7
6
1
register address
Read Response Packet:
7
6
0
register address
Write Command:
7
6
0
register address
1. byte
SMCS332SpW
User Manual
0
1. byte
0
1. byte
0
write data
– All Rights Reserved – Copyright per DIN 34 –
ignored
EOP
2. - n. byte
register value
EOP
2. byte
2. byte
3. - n. byte
EADS Astrium GmbH, ASE2
Doc No: SMCS_ASTD_UM_100
Issue:
1.4
Updated: 9-Sep-2006
Page:
48 of 131
ignored
EOP
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