The bVME register class is used for block mode VME accesses.

The register value is a sequence of data items. The first data item corresponds to the VME address obtained by adding the -a and -o attribute values. Subsequent data items are obtained by incrementing the VME address by 2 or 4 bytes as determined by the -d attribute.

The class accepts data values in decimal, hexadecimal or binary format.

All address variables are VME addresses and are thus expressed in units of bytes (8 bits).

Register values for the bVME class are text strings.

Attributes :-

-a    VME base address

specifies the start address of the data area as a VME address.

-o    offset

specifies the address offset of the block access relative to the base of the data area.

-w    width of VME address in bits. Options are 16; 24; 32.

specifies the address width required for accesses to the VME hardware.

-d    width of VME data access in bits. Options are 16; 32.

specifies the data width required for accesses to the VME hardware.

-u    use. Options are d (data); p (program).

specifies the use required for accesses to the VME hardware.

-m    mode. Options are n (non-privileged); s (supervisory).

specifies the mode required for accesses to the VME hardware.

-m    VME address modifier.

specifies the address modifier required for accesses to the VME hardware.

If a numeric value is supplied this is taken to be a VME address modifier and the -u and -w attributes are ignored. Otherwise the -m, -u and -w attributes are taken to define the VME address modifier.

-p    access permission (rw, ro, wo)

specifies the data access modes permitted to the VME hardware. Options are ro (read only); wo (write only); rw (read-write).

-z    data format

specifies the data format to be used by READ operations. Data can be return in decimal (d), hexadecimal (x) or binary (b). The default is hexadecimal.

-l    length

specifies the length of the data block in units of data items.

-i    initial value

specifies the data value to be used by the INITIALISE operation. The register must also have write permission.

default attributes     :   -a 0x0 -o 0x0 -w 32 -d 32 -u d -m n -p rw -l 1 -z x
The default address modifier is thus 0x09 (A32 data access non-privileged)
The default attribute value is used for any attribute not defined by a write-attributes procedure call.

data for write operations may be supplied in any format but the data format attribute (-z) will determine the format used when returning data for read operations.

The absolute VME address of the start address of a block access is given by data area base address + block offset.

The WRITE and READ operations transfer a number (given by the -l attribute) of data words (of width given by the -w attribute).
The INITIALISE operation writes the data value given by the -i attribute to a number of locations given by the -l attribute. This is useful for setting all locations in a data buffer to a given value.