Communication Block
UG0331 User Guide Revision 15.0
600
17.5.5
Word Data Register
This register writes a word (32 bits) to the Transmit FIFO or reads a word from the Receive FIFO. If the
Transmit FIFO has less than 4 spaces available at the time of a write, an OVERFLOW will be set in the
register. Similarly, if Receive FIFO has less than 4 bytes available at the time of a read, an
UNDERFLOW will be generated.
The LSB is transferred on the DATA bus first. When the
register is written, the command bit
(Bit 8 on DATA) is set to 0, indicating that it is data. Writes to this register automatically set the SIZETX to
1 (4 bytes) and reads set the SIZERX to 1 (4 bytes).
17.5.6
Frame/Command Byte Register
This register writes a byte to the Transmit FIFO or reads a byte from the Receive FIFO. If the Transmit
FIFO is full at the time of a write, an OVERFLOW will be set in the
register. Similarly, if Receive
FIFO is empty at the time of a read, an UNDERFLOW will be generated.
When the FRAME_START8 register is written, the command bit (Bit 8 on DATA) is set to 1, indicating the
start of a frame, that is, the command byte. Writes to this register automatically set the SIZETX to 0 (1
byte), and reads set the SIZERX to 0 (1 byte). The
register bit 7 indicates that this byte is a
command.
17.5.7
Frame/Command Word Register
This register writes a word (32-bits) to the Transmit FIFO or reads a word from the Receive FIFO. If the
Transmit FIFO has less than four spaces available at the time of a write, an OVERFLOW will be set in
register. Similarly, if Receive FIFO has less than four bytes available at the time of a read, an
UNDERFLOW will be generated.
The least significant bit (LSB) is transferred on the DATA bus first. When the
register
is written, the command bit is set to 1, indicating the start of a frame, that is, command byte. The
command bit (Bit 8 on DATA) will be set on the first byte for writes.
Writes to this register automatically sets the SIZETX to 1 (4 bytes) and reads set the SIZERX to 1
(4 bytes). The
register bit 7 indicates that this word is a command.
Table 598 •
DATA32
Bit
Number Name
R/W Reset Value
Description
[31:0]
DATA32
R/W 0x00000000
Write: Writes a word to the MSS COMM_BLK Transmit FIFO
Read: Read a word from the MSS COMM_BLK Receive FIFO
Table 599 •
FRAME_START8
Bit
Number Name
R/W
Reset Value
Description
[7:0]
FRAME_START8 R/W
0x00
Write: Writes byte to the MSS COMM_BLK transmit FIFO
Read: Read a byte from the MSS COMM_BLK receive FIFO
Table 600 •
FRAME_START32
Bit
Number Name
R/W Reset Value Description
[31:0]
FRAME_START32 R/W 0x00000000
Write: Writes a word to the MSS COMM_BLK transmit FIFO
Read: Reads a word from the MSS COMM_BLK receive FIFO