SAB 82525
SAB 82526
SAF 82525
SAF 82526
The activities during frame transmission (supposed two frames, 18 bytes and 52 bytes) is
shown in figure 35.
Frame 1
18 Bytes
Frame 2
Serial
Interface
32 Bytes
20 Bytes
ITF
ITF
HSCX
CPU
Interface
. . .
. . .
. . .
WR
18 Bytes
XTF
XME
WR
32 Bytes
XTF
WR
20 Bytes
XTF
XTF + XME
XPR
XPR
XPR
XPR
ITD00249
Figure 35
Continuous Frames Transmission Sequence Example
DMA Mode
Prior to the data transmission, the length of the next frame to be transmitted must be
programmed via the Transmit Byte Count Registers (XBCH, XBCL). The resulting byte count
equals the programmed value plus one byte, i.e. since 12 bits are provided via XBCH, XBCL
(XBC11. . .XBC0) a frame length of 1 up to 4096 bytes (4 Kbytes) can be selected.
After this, data transmission can be initiated by command (XTF or XIF). The HSCX will then
autonomously request the correct amount of write bus cycles by activating the DRQT line.
Depending on the programmed frame length, block data transfers of
n × 32-bytes + remainder (n = 0, 1,…128)
are requested everytime a 32-byte FIFO half (transmit pool) is empty and accessible to the
DMA controller.
Semiconductor Group
74
SIEMENS [ Siemens Semiconductor Group ]
