Rainbow Electronics DS3170 - Manual (Page 157)

DS3170 DS3/E3 Single-Chip Transceiver
157 of 233
Bit 1: Transmit FCS Processing Disable (TFPD) – This bit controls whether or not an FCS is calculated and
appended to the end of each packet. When 0, the calculated FCS bytes are appended to the end of the packet.
When 1, the packet is transmitted without an FCS.
Bit 0: Transmit FIFO Reset (TFRST) – When 0, the Transmit FIFO will resume normal operations, however, data
is discarded until a start of packet is received after RAM power-up is completed. When 1, the Transmit FIFO is
emptied, any transfer in progress is halted, the FIFO RAM is powered down, and all incoming data is discarded (all
TFDR register writes are ignored).
Register Name:
HDLC.TFDR
Register Description: HDLC Transmit FIFO Data Register
Register Address: 0A2h
Bit
# 15 14 13 12 11 10 9 8
Name TFD7 TFD6 TFD5 TFD4 TFD3 TFD2 TFD1 TFD0
Default
0 0 0 0 0 0 0 0
Bit
# 7 6 5 4 3 2 1 0
Name -- -- -- -- -- -- -- TDPE
Default 0 0 0 0 0 0 0 0
Note: The FIFO data and status are loaded into the Transmit FIFO when the Transmit FIFO Data (TFD[7:0]) is
written (upper byte write). When read, the value of these bits is always zero.
Bits 15 to 8: Transmit FIFO Data (TFD[7:0]) – These eight bits are the packet data to be stored in the Transmit
FIFO. TFD[7] is the MSB, and TFD[0] is the LSB. If bit reordering is disabled, TFD[0] is the first bit transmitted, and
TFD[7] is the last bit transmitted. If bit reordering is enabled, TFD[7] is the first bit transmitted, and TFD[0] is the
last bit transmitted.
Bit 0: Transmit FIFO Data Packet End (TDPE) – When 0, the Transmit FIFO data is not a packet end. When 1,
the Transmit FIFO data is a packet end.
Register Name:
HDLC.TSR
Register Description: HDLC Transmit Status Register
Register Address: 0A4h
Bit
# 15 14 13 12 11 10 9 8
Name -- -- TFFL5 TFFL4 TFFL3 TFFL2 TFFL1 TFFL0
Bit
# 7 6 5 4 3 2 1 0
Name -- -- -- -- -- TFF TFE THDA
Bits 13 to 8: Transmit FIFO Fill Level (TFFL[5:0]) – These six bits indicate the number of eight byte groups
available for storage (do not contain data) in the Transmit FIFO. E.g., a value of 21 (15h) indicates the FIFO has
168 (A8h) to 175 (AFh) bytes are available for storage.
Bit 2: Transmit FIFO Full (TFF) – When 0, the Transmit FIFO contains 255 or less bytes of data. When 1, the
Transmit FIFO is full.
Bit 1: Transmit FIFO Empty (TFE) – When 0, the Transmit FIFO contains at least one byte of data. When 1, the
Transmit FIFO is empty.
Bit 0: Transmit HDLC Data Storage Available (THDA) – When 0, the Transmit FIFO has less storage space
available in the Transmit FIFO than the Transmit HDLC data storage available level (TDAL[4:0]). When 1, the
Transmit FIFO has the same or more storage space available than the Transmit FIFO HDLC data storage available
level.