Rainbow Electronics DS31256 - Manual (Page 78)

DS31256
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Bit 14/Indirect Access Read/Write (IARW). When the host wishes to read data from the internal receive block
pointer RAM, the host should write this bit to 1. This causes the device to begin obtaining the data from the block
location indicated by the BLKID bits. During the read access, the IAB bit is set to 1. Once the data is ready to be
read from the RFBP register, the IAB bit is set to 0. When the host wishes to write data to the internal receive
block pointer RAM, the host should write this bit to 0. This causes the device to take the data that is currently
present in the RFBP register and write it to the channel location indicated by the BLKID bits. When the device
completes the write, the IAB is set to 0.
Note: The RFSBP is write-only memory. Once this register has been written to and the operation has started, the
DS31256 internal state machine changes the value in this memory.
Bit 15/Indirect Access Busy (IAB). When an indirect read or write access is in progress, this read-only bit is set
to 1. During a read operation, this bit is set to 1 until the data is ready to be read. It is set to 0 when the data is
ready to be read. During a write operation, this bit is set to 1 while the write is taking place. It is set to 0 once the
write operation completes.
Register Name:
RFBP
Register Description: Receive FIFO Block Pointer
Register Address:
0914h
Bit # 7 6 5 4 3 2 1 0
Name RBP7 RBP6 RBP5 RBP4 RBP3 RBP2 RBP1 RBP0
Default
Bit # 15 14 13 12 11 10 9 8
Name n/a n/a n/a n/a n/a n/a RBP9 RBP8
Default
Note: Bits that are underlined are read only, all other bits are read-write.
Bits 0 to 9/Block Pointer (RBP0 to RBP9). These bits indicate which of the 10242 blocks is the next block in the
link-list chain. A block is not allowed to point to itself.
0000000000 (000h) = block 0 is the next linked block
0111111111 (1FFh) = block 511 is the next linked block
1111111111 (3FFh) = block 1023 is the next linked block
Register Name:
RFHWMIS
Register Description: Receive FIFO High-Watermark Indirect Select
Register Address:
0920h
Bit # 7 6 5 4 3 2 1 0
Name HCID7 HCID6 HCID5 HCID4 HCID3 HCID2 HCID1 HCID0
Default 0 0 0 0 0 0 0 0
Bit # 15 14 13 12 11 10 9 8
Name IAB IARW n/a n/a n/a n/a n/a n/a
Default 0 0 0 0 0 0 0
Note: Bits that are underlined are read-only; all other bits are read-write.
Bits 0 to 7/HDLC Channel ID (HCID0 to HCID7)
00000000 (00h) = HDLC channel number 1
11111111 (FFh) = HDLC channel number 256