Commodore PET User Manual page 436

Table
G-,.
PET Memory Map (Rev 2 ROMs) (Continued)
Memory Address Semple Value
Decimal Hexadecimal Decimal
Hexadecimal
Description
59457
E841
59458
E842
59459
E843
59460-59461
E844-E845
59462-59463
E846-E847
59464
E848
Perallel User Port VIA
(59456-594711
01
00
FF
1E
00
FE
DE
C8
FF65
71
62AO
o
14
255
30
o
200
254
1/0 Port B
207 =
*
2 cassette motor on
223 =
*
2 cassette motor off
WAil 59456.23.23 waits for vertical
retrace of display
Bit 1=PB1 (NFRD on IEEE connector) out-
put line
Bit 3=P83 (AlN on IEEE connector) out-
put line
1/0 Port A with handshaking
Data Direction register for 1/0 Port B
Data Direction register for 1/0 Port A
For each bit 1=output. O=input
=0 ail input
=255 ail output
(Law. high arder) Read limer 1 Counter;
writeto limer 1 Latch and (high byte)
initiate count
(Law. high arder) Read limer 1 Latch
Read limer 2 Counter low byte and reset
interrupt; write ta limer 2 low byte
PEEK (594641 Clock decrements every
microsecond
POKE 59464.n sets SR rate of shift from
high (n=O) ta low (n=255) for music
from User Port.
Read limer 2 Counter high byte; write ta
limer 2 high byte and reset interrupt.
PEEK (594651 Clock decrements every
millisecond
Seriai 1/0 Shift register (SR)
POKE 59466.15 or 51 or 85 ta generate
square wave output at CB2 for playing
music fram User Port.
Auxiliary Control register.
= 16 Sets SR ta free-running mode for
music fram User Port.
=0 for proper operation of tape drive
Peripheral Control register
= 12 for graphies on shifted characters
= 14 for lower-case letters on shifted
characters
o
00 Interrupt Flag register
128 80 Interrupt Enable register
255 FF 1/0 Port A without handshaking
Page 241-256 Operating System (61440-65535)
File Control
25248
65381
113
E849
E848
E840
E84C
E84D
E84E
E84F
E84A
FOB6-FlOO
59456
59465
59468
59466
59469
59470
59471
59467
61622-61904
61905-63532 F1 D1-F82C
5t.'tin9 Addr.ss Function
61905 Fl Dl Get a character
(without cursor)
61921 F1E1 Input a character
(wlth cursor)
423