pc87317vul National Semiconductor Corporation, pc87317vul Datasheet - Page 132

• Manufacturer Part Number: pc87317vul
• Description: Pc87317vul/pc97317vul Superi/o Plug And Play Compatible With Acpi Compliant Controller/extender
• Manufacturer: National Semiconductor Corporation

www.national.com
The parameters used by this command are undefined after
power up, and are unaffected by any reset. Therefore, soft-
ware should always issue a SPECIFY command as part of
an initialization routine to initialize these parameters.
Terminating this command does not generate an interrupt.
Command Phase
Second Command Phase Byte
Bits 3-0 - Delay After Processing Factor
Data Transfer
Data Transfer
Data Transfer
7
0
Step Rate Time (SRT)
Rate (bps)
Rate (bps)
These bits specify a factor that is multiplied by a con-
stant to determine the delay after command processing
ends, i.e., from termination of a command until the drive
motor is no longer selected.
Rate (bps)
TABLE 5-26. STEP Time Interval Calculation
500 K
300 K
250 K
500 K
300 K
250 K
500 K
300 K
250 K
1 M
1 M
1 M
6
0
Delay Before Processing
TABLE 5-25. Constant Multipliers for Delay Before Processing Factor and Delay Ranges
TABLE 5-24. Constant Multipliers for Delay After Processing Factor and Delay Ranges
5
0
.
Calculation of Time
Constant Multiplier
Constant Multiplier
(16
(16
(16
(16
4
0
Interval
SRT) x 1.67
80 / 3
10 / 3
SRT) x 2
SRT) / 2
16
32
8
1
1
4
SRT)
Bit 7 of MODE (TMR) = 0
Bit 7 of MODE (TMR) = 0
3
0
Delay After Processing
2
0
Range (msec)
Permitted Range (msec)
Permitted Range (msec)
1.67 - 26.7
Permitted
0.5 - 8
1 0 16
2 - 32
1
1
26.7 - 427
3.3 - 427
16 - 256
32 - 512
4 - 512
8 -128
1 -128
1 -128
DMA
0
1
132
Bits 7-4 - STEP Time Interval Value (SRT)
Third Command Phase Byte
Bit 0 - DMA
The value of the Motor Timer Values (TMR) bit (bit 7) of
the second command phase byte in the MODE com-
mand determines which group of constants and delay
ranges to use. See “Bit 7 - Motor Timer Values (TMR)”
on page 119.
The specific constant that will be multiplied by this factor
to determine the actual delay after processing for each
data transfer rate is shown in TABLE 5-24 "Constant
Multipliers for Delay After Processing Factor and Delay
Ranges" on page 132.
Use the smallest possible value for this factor, except 0,
i.e., 1. If this factor is 0, the value16 is used.
These bits specify a value that is used to calculate the
time interval between successive STEP signal pulses
during a SEEK, IMPLIED SEEK, RECALIBRATE, or
RELATIVE SEEK command.
TABLE 5-26 "STEP Time Interval Calculation" on page
132 shows how this value is used to calculate the actual
time interval.
This bit selects the data transfer mode in the execution
phase of a read, write, or scan operation.
Data can be transferred between the microprocessor
and the controller during execution in DMA mode or in
non-DMA mode, i.e., interrupt transfer mode or software
polling mode.
See Section 5.4.2 "Execution Phase" on page 104 for a
description of these modes.
0: DMA mode is selected.
1: Non-DMA mode is selected.
Constant Multiplier
Constant Multiplier
2560 / 3
160 / 3
1024
512
512
32
32
64
Bit 7 of MODE (TMR) = 1
Bit 7 of MODE (TMR) = 1
Permitted Range (msec)
Permitted Range (msec)
1024 -16384
853 - 13653
512 - 8192
512 - 8192
32 - 4096
32 - 4096
53 - 6827
64 - 8192