ISA-to-PC-Card (PCMCIA) Controllers
—
PD6710/
’
22
Datasheet
85
Bits 7:6
—
Setup Prescalar Select
This field chooses one of four prescalar values
N
pres
that are combined with the value of the Setup
Multiplier Value (bits 5:0) to control the length of setup time before a command becomes active.
11.2
Command Timing 0
–
1
There are two separate Command Timing registers, each with identical fields. These registers are
located at the following indexes:
Index
3Bh
3Eh
Command Timing
Command Timing 0
Command Timing 1
The Command 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
) active time will be, in terms of the
number of internal clock cycles.
The overall command timing length
C
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 timing length
according to the following formula:
C
= (
N
pres
×
N
val
) + 1
The value of
C
, representing the number of internal clock cycles for a command, is then multiplied
by the internal clock
’
s period to determine the command active 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:
Command Timing 0
–
1
Index:
3Bh, 3Eh
Register Per:
socket
Register Compatibility Type:
365
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Command Prescalar Select
Command Multiplier Value
RW:00
RW:000110/001111
1
1. Timing set 0 (index 3Bh) resets to 06h for socket timing equal to standard AT-bus-based cycle times. Timing set 1 (3Eh)
resets to 0Fh for socket timings equal to standard AT-bus timing using one additional wait state.