W86L387D Datasheet, PDF (14/25 Pages) Winbond – Winbond Host Interface Memory StickTM Bridge

W86L387D
7.2 DMA Access
PRELIMINARY
DMA request XDRQN is used to notify the Host that the Host should write data to the transmit data
buffer or read data from the receive data buffer in data write to the card or data read from the card.
During data transmit to the card, the XDRQN will active if the data write command has been transfer to
the card and the transmit data buffer have not enough data to transmit to the card. The XDRQN will
not active if the transmit data buffer have enough data to transmit to the card.
During data receive from the card, the XDRQN will active if the data read command has been transfer
to the card and the data have been received in the receive data buffer. The XDRQN will not active if
the data read command has been executed completely and the receive data buffer is read out.
There are two types of DMA acknowledge waveform, the first type is configured if DAKEN = low,
XDAKN is ignore and XDRQN will inactive after each access receive or transmit data buffer, the
XDRQN will re-active after four clock later. Figure 7-6 shows the waveform of DMA access receive
data buffer in DAKN = low. The second type is configured if DAKEN = high, XDAKN is used to count
the transfer count of the data buffer, XDRQN will hold at active state until the data has been
transferred completely. Figure 7-7 is the waveform of DMA access transmit data buffer in DAKN =
high.
System clock
A[3:1]
010
010
D[15:0]
XCSN
XRDN
XDRQN
XDAKN
Fig. 7-6 DMA Access Receive Data Buffer (DAKEN = low).
- 11 -
Publication Release Date: July 2001
Revision 0.50