Maxtor 10K III WRITE BUF F ER Com ma nd -Field Descriptions

WRITE BUF F ER Com ma nd -Field Descriptions

Mode Fo ur modes are support ed by the dr ive; Combine d Header and Data, Data Only, Download

Microcode and Save, and Wri te Data from Echo Buffer. The perm issib le value s for Buffe r

ID, Buffer Offset are as follows:

0000b

Combined Header and Data – In this mode, the dat a to be tra nsferred is preceded by a 4-

byte header that contains reserved bytes that must be set to 0. The resulting descriptor and

data are fetched from the initiator during the command's data-out buffer transfer and, after

the descriptor has b een validated, only t h e data is written to the controller' s me mor y.

must be 0

must b e set to be tween 0 and 516 (4 bytes of header and up t o 512

bytes of data).

0010b

Data Only– In this mode, the data-out buffer transfer contains buffer data. Data is written

to the drive's buffer star ting at the location specified by the Buffer ID and Buffer Offse t.

. When non-zer o, the value sp ecifies a specific track li ne in the con troller’s c ache.

If Buffer ID of zero is specified, the buffer referenced is the same as if Buffer ID of one were

specified.

. W hen non-zer o, the valu e can range f rom 0 to one les s than th e number o f

sectors/ track multiplied by 512. This value must be either a zero or a multiple of 512.

. This value must be a multiple of 512. The maximum value for this

field is one more than the number of sectors/track times 512. The minimum value is 0.

0101b

In this mode, a microcode image is transferred to the drive,

and if valid, is saved in the controller's non-volatile memory. This image must be transferred

with al l buff ers of the same size (t he last buff er of the transfer canno t be of a diff erent siz e)

and the buffer size must be a multiple of 512. Most images are mult iples of 512 and 1K. In

that case, it is safe to have 512 byte transfers or 1K t ransfers. For exam ple, if the image

size is 3 69K, then 738 51 2-byte buffers can be trans ferred or 369 1K byte buffers can be

transferred. It is also poss ible to transfer the image in one large buf fer .

The controller does a hard reset on command completion. In Download Microcode and Save

mode, the other Comman d Descriptor Blocks are support ed as follows:

– Undefined and ignored.

– The offse t of the b uffer being transferr ed. For example: for 51 2 byte trans-

fers use 0, 512, 1024, 1536,.... For 1K byte transfer s use 0, 1024, 2048, 3072...

– Must be the si ze of the buff er bei ng transferred.

(0111b) This mode act s the same as mode 0101b but

is restricted to sending the bytes in sequential order.

1010b

Write Data from Echo Buffer

In thi s mod e, the host transfers data and stores it in an echo buffer. The data wi ll be pre-

served in the echo buffer unless there i s an intervening command.

Ignored.