Apple-2gs-SW/itty-bitty-vtty
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Kelvin Sherlock 2021-10-17 16:51:41 -04:00
parent 31394e84c4
commit 892aed32f4
2 changed files with 15 additions and 0 deletions
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5
apple2gs.equ.S
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@ -7,6 +7,10 @@ KBD equ $c000
VGCINT equ $c023
SCANINT equ $c032
RDCARDRAM equ $c003
RDMAINRAM equ $c002
WRCARDRAM equ $c005
WRMAINRAM equ $c004
* modem port / printer port
@ -27,3 +31,4 @@ IRQ1SEC equ $e10054
IRQQTR equ $e10038
IRQVBL equ $e10030
IRQSND equ $e1002c

10
vt100.modem.S
View File

@ -14,6 +14,16 @@ SCCBDATA equ $c03a
SCCADATA equ $c03b
*
* scc speed:
*
* time constant = ( clock / (2 * clock mode * baud rate)) - 2
* baud rate = clock / ( 2 * clock mode * (time constant + 2))
*
* clock mode = 1x, 16x, 32x, or 64x (selected via write register 4 bits 6/7)
* clock = 3.6864 MHz crystal (scc runs at 14.31818 / 4 = ~ 3.58 Mhz)
* time constant = write register 12 (low) + 13 (high)
init_modem ent
* sep #$30