spd6722qcce Intel Corporation, spd6722qcce Datasheet - Page 35

• Manufacturer Part Number: spd6722qcce
• Description: Isa-to-pc-card Pcmcia Controllers
• Manufacturer: Intel Corporation

4.1.10
4.1.11
.
Datasheet
Table 9. 16-Bit Mode Operation
Table 10. 8-Bit Mode Operation
bit 5 is ‘0’), system software can determine the card’s operating voltage range and then power-up
the socket and initialize the card (or simply initialize the card if programmed for automatic power-
on (Power Control register bit 5 is ‘1’ and Extension Control 1 register bit 1 is ‘1’)).
Write FIFO
To increase performance when writing to PC Cards, two, independent, four-word-deep write
FIFOs are used. Writes to PC Cards will complete without wait states until the FIFO is full.
Register states should not be changed until the write FIFO is empty.
Bus Sizing
The PD67XX incorporates logic to automatically detect its connection to 8- or 16-bit buses. This is
accomplished by sensing SBHE* input activity. If the SBHE* pin is always high (that is, tied to
ISA_VCC), the PD67XX operates in 8-bit mode where all transfers occur on the lower data bus,
bits 7:0. Any occurrence of the SBHE* going low triggers the PD67XX to operate thereafter as a
16-bit device. 16-bit operation of the PD67XX is properly triggered when the SBHE* input is
connected to the system’s SBHE* signal. When the PD67XX is operating in 16-bit mode, all ISA
bus transactions are 16-bit whenever possible, even if installed PC cards only support 8-bit
transfers. In 16-bit mode, the signals SBHE* and SA0 are used to specify the width of the data
transfer and the location of data on the bus (which byte lane has the data) during 8-bit transfers.
The possible combinations for SBHE* and SA0 are shown in
Typically, there are three types of data transfers to and from the PD67XX:
Word
Upper Byte/Odd Address
Low Byte/Even Address
Not Valid
Even Address
Odd Address
1. The SBHE* signal is pulled up. If the SBHE*
•
•
signal remains high, thePD67XX causes all
transfers to occur on D[7:0] only
16-Bit Transfer from 16-Bit Processor — The CPU puts the address on the bus. Then the
PD67XX identifies the address on the bus as either an 8- or 16-bit transfer. If the transfer is
identified as 16-bit, the host acknowledges with the appropriate signal, either MEMCS16* or
IOCS16*. Data is transferred to/from the data bus as a word on both byte lanes.
8-Bit Transfer from 16-Bit Processor — The CPU puts the address on the bus. Then the
PD67XX identifies the address on the bus as either an 8- or 16-bit transfer. In this case, the
transfer is identified as an 8-bit transfer. The host queries SA0 and SBHE* to determine the
16-Bit Mode Transfer Types
8-Bit Mode Transfer Types
1
ISA-to-PC-Card (PCMCIA) Controllers — PD6710/’22
SBHE*
SA0
0
0
1
1
0
1
SA0
0
1
0
1
Table 9
and
Table 10
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