PD6710/
’
22
—
ISA-to-PC-Card (PCMCIA) Controllers
86
Datasheet
Bits 5:0
—
Command Multiplier Value
This field indicates an integer value
N
val
from 0 to 63; it is combined with a prescalar value (bits
7:6) to control the length that a command is active.
Bits 7:6
—
Command Prescalar Select
This field chooses one of four prescalar values
N
pres
that are combined with the value of the
Command Multiplier Value (bits 5:0) to control the length that a command is active.
11.3
Recovery Timing 0
–
1
There are two separate Recover Timing registers, each with identical fields. These registers are
located at the following indexes:
Index
3Ch
3Fh
Recovery Timing
Recovery Timing 0
Recovery Timing 1
The Recovery Timing register for each timing set controls how long a PC Card cycle
’
s command
(that is, -OE, -WE, -IORD, -IOWR; see
Table 2 on page 20
) recovery will be, in terms of the
number of internal clock cycles.
The overall command recovery timing length
R
is programmed by selecting a 2-bit prescaling
value (bits 7:6 of this register) representing weights of 1, 16, 256, or 8192, and then selecting a
multiplier value (bits 5:0) to which that prescalar is multiplied to produce the overall command
recovery timing length according to the following formula:
R
= (
N
pres
×
N
val
) + 1
The value of
R
, representing the number of internal clock cycles for command recovery, is then
multiplied by the internal clock
’
s period to determine the command recovery time (see
“
PC Card
Bus Timing Calculations
”
on page 109
for further discussion).
00
Npres = 1
Npres = 16
Npres = 256
Npres = 8192
01
10
11
Register Name:
Recovery Timing 0
–
1
Index:
3Ch, 3Fh
Register Per:
socket
Register Compatibility Type:
365
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Recovery Prescalar Select
Recovery Multiplier Value
RW:00
RW:000011