Tandy 1000 HX Technical Reference Manual page 133

8259A
Initialization Command Word 4 (ICW4)
SFNM: If SFNM = 1 the special fully nested mode
is programmed.
BUF: If BUF = 1 the buffered mode is pro-
grammed. In buffered mode 5P/ER be-
comes an enable output and the master/
slave determination is by M/S.
M/S: If buffered mode is selected: M/S = 1
means the 8259A is programmed to be a
master, M/S = 0 means the 8259A is pro-
grammed to be a slave. If BUF = 0, M/S
has no function.
AEOI: If AEOI = 1 the automatic end of interrupt
mode is programmed.
JLIPM: Microprocessor mode: /xPM = 0 sets the
8259A for MCS-80, 85 system operation,
j m PM = 1 sets the 8259A for 8086 system
operation.
Figure 7. Initialization Command Word Format
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