Group numbers less than 256 correspond to standard group format; group numbers of 256 upwards correspond to extended group format. Within any one group the format must be the same, i.e. group numbers must be in one format range only (0--255 or 256--1023). A group consists of all the parameters associated with one device, e.g. a germanium detector, would have an associated energy word, ballistic deficit correction words, etc. The structure of all devices having the same sets of associated parameters can be specified concisely using group format,

*FORMATS 
GE[2,4:10,19,23:26] (E1,E2,TAC,TACBD)
CLOVER[51:74] (BGOE,BGOT,BGOP,
                 A1,A2,A3,A4,
                 B1,B2,B3,B4,
                 C1,C2,C3,C4,
                 D1,D2,D3,D4)
CLOVER1[101:124] (E20, E4TAG1:3, E4DAT1:13)
CLOVER2[151:174] (E20, E4TAG1:3, E4DAT1:13, E4TAG2:3,  E4DAT2:13)
TRACES[256:300]  ( pulse(128) )

where the group name GE represents a group type consisting of 4 items: E1, E2, TAC and TACBD. defined for group numbers 2,4,5,6,7,8,9,10,19,23,24,25,26.

CLOVER has 19 items defined for group numbers 51 to 74 inclusive, whereas CLOVER1 and CLOVER2 are examples of groups which use bit fields to specify sections of the item data words for ease of access in the *COMMANDS section.

Within the commands section the syntax used to refer to a single item of a particular group would be:

 GE[13].E1

would refer to item E1 of group 13.

 CLOVER[153].E4TAG2

would refer to the item E4TAG2, i.e. to the top 3 bits of the third data word, of group 153.

If only one group number is defined for a single group name, in *FORMATS, then it may be referenced in the commands section without specifying the group number, e.g.

TRIG[255] (S1,S2)

would be referenced as TRIG.S2 to access the second item of group TRIG.

traces[256:300] ( pulse(128) )

would be referenced as TRACES.PULSE(I) to access the i'th PULSE item of group TRACES.

e.g.
i = 17
s = traces[256].pulse(i)