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SAB 82532/SAF 82532
Detailed Register Description
Semiconductor Group
115
07.96
Transmit FIFO (XFIFO)
Access: write
address: ch-A: 00 ... 1F
H
ch-B: 40 ... 5F
H
Writing data to the XFIFO can be done in 8-bit (byte) or 16-bit (word) access depending
on the selected bus interface mode. The LSB is transmitted first.
Interrupt Mode
Selected if DMA bit in XBCH is set to ‘zero’.
Up to 32 bytes/16 words of transmit data can be written to the XFIFO following an XPR
(or ALLS) interrupt.
DMA Mode
Selected if DMA bit in XBCH is set to ‘one’.
Prior to any data transfer, the actual
byte
count of the frame to be transmitted must
be written to the XBCH, XBCL registers by the user.
If data transfer is then initiated via the CMDR register (command XTF or XIF), the
ESCC2 autonomously requests the correct amount of block data transfers
(n
×
BW + Remainder; BW = 32 or 16; n = 0, 1, …).
Note: Addresses within the address space of the FIFO’s all point to the current data
word/byte, i.e. the current data byte can be accessed with any address within the
32-byte range.
In HDLC mode (no extended transparent mode) 32 bytes have to be written to the
FIFO when only XTF command is set afterwards. There is no restriction when XTF
and XME command is set afterwards.
Status Register (STAR)
Access: read
address: ch-A: 20
H
ch-B: 60
H
Value after RESET: 48
H
7
0
STAR
XDOV
XFW
XRNR
RRNR
RLI
CEC
CTS
WFA
XDOV …
Transmit Data Overflow
More than 32 bytes have been written to the XFIFO.
This bit is reset by:
– a transmitter reset command XRES
– or when all bytes in the accessible half of the XFIFO have been
moved into the inaccessible half.
Transmit FIFO Write Enable
Data can be written to the XFIFO.
XFW …
HDLC Mode