Commodore VIC-20 Programmer's Reference Manual page 242

clears the corresponding bit In the IER. If this bit is a 1 during this
register, each 1 in bits 0-6 will set the corresponding IER bit.
d TIMER 1 time-out enable
e TIMER 2 time-out enable
f CB1 interrupt enable
g CB2 interrupt enable
h Shift interrupt enable
i CA1 interrupt enable
j CA2 interrupt enable
kkkkkkkk: PORT A
This is similar to BBBBBBBB, except that the handshaking lines
(CA1 and CA2) are unaffected by operations on this port.
I
I
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