PC97338VLJ datasheet(117/221 Pages) NSC

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TABLE 58. Constant Multipliers for Delay After Processing Factor and Delay Ranges

TABLE 59. Constant Multipliers for Delay Before Processing Factor and Delay Ranges

Data Transfer

Rate (bps)

Bit 7 of MODE (TMR) = 0

Bit 7 of MODE (TMR) = 1

Constant Multiplier Permitted Range (msec) Constant Multiplier Permitted Range (msec)

1 M

8 -128

512

512 - 8192

500 K

16 - 256

512

512 - 8192

300 K

80 / 3

26.7 - 427

2560 / 3

853 - 13653

250 K

32 - 512

1024

1024 -16384

Data Transfer

Rate (bps)

Bit 7 of MODE (TMR) = 0

Bit 7 of MODE (TMR) = 1

Constant Multiplier Permitted Range (msec) Constant Multiplier

Permitted Range

(msec)

1 M

1 -128

32 - 4096

500 K

1 -128

32 - 4096

300 K

10 / 3

3.3 - 427

160 / 3

53 - 6827

250 K

4 - 512

64 - 8192

Bits 7-4 - STEP Time Interval Value (SRT)

These bits specify a value that is used to calculate

the time interval between successive STEP signal

pulses during a SEEK, IMPLIED SEEK, RECALI-

BRATE, or RELATIVE SEEK command.

Table 60 shows how this value is used to calculate

the actual time interval.

TABLE 60. STEP Time Interval Calculation

Third Command Phase Byte

Bit 0 - DMA

This bit selects the data transfer mode in the exe-

cution phase of a read, write, or scan operation.

Data can be transferred between the microproces-

sor and the controller during execution in DMA

mode or in non-DMA mode, i.e., interrupt transfer

mode or software polling mode.

See “Execution Phase” on page 85 for a descrip-

tion of these modes.

0 - DMA mode is selected.

1 - Non-DMA mode is selected.

Bits 3-0 - Delay Before Processing Factor

These bits specify a factor that is multiplied by a

constant to determine the delay before command

processing starts, i.e., from selection of a drive

motor until a read or write operation starts.

The value of the Motor Timer Values (TMR) bit (bit

7) of the second command phase byte in the

MODE command determines which group of con-

stants and delay ranges to use. See “Bit 7 - Motor

Timer Values (TMR)” on page 101.

The specific constant that will be multiplied by this

factor to determine the actual delay before pro-

cessing for each data transfer rate is shown in Ta-

ble 59.

Use the smallest possible value for this factor, ex-

cept 0, i.e., 1. If this factor is 0, the value128 is

used.

Execution Phase

Internal registers are written.

Result Phase

None.

Data Transfer

Rate (bps)

Calculation of

Time Interval

Permitted

Range (msec)

1 M

(16

− SRT) / 2

0.5 - 8

500 K

(16

− SRT)

1 - 16

300 K

(16

− SRT) x 1.67

1.67 - 26.7

250 K

(16

− SRT) x 2

2 - 32

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