Apple-2-HW/analog-firmware
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Timing tweaks

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This commit is contained in:
David Kuder 2023-05-04 20:54:15 -04:00
parent 4586bb8638
commit 3ee0061fdc
1 changed files with 17 additions and 17 deletions
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34
common/abus-4ns.pio
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@ -21,19 +21,19 @@
; x - select Data, active low
.wrap_target
next_bus_cycle:
set PINS, 0b011 ; enable AddrHi tranceiver
wait 1 GPIO, PHI0_GPIO ; wait for PHI0 to rise. Data propagation through the transceiver should
; be complete by the time this happens.
set PINS, 0b111 ; disable tranceivers
wait 1 GPIO, PHI0_GPIO [5] ; wait for PHI0 to rise.
set PINS, 0b011 [5] ; enable AddrHi tranceiver and delay for transceiver propagation delay (24ns)
in PINS, 8 ; read AddrHi[7:0]
set PINS, 0b101 [12] ; enable AddrLo tranceiver and delay for transceiver propagation delay
set PINS, 0b101 [5] ; enable AddrLo tranceiver and delay for transceiver propagation delay (24ns)
in PINS, 8 ; read AddrLo[7:0]
jmp PIN, read_cycle ; jump based on the state of the R/W pin
write_cycle:
; the current time is P0+82ns (P0 + 10ns + 2 clocks (input synchronizers) + 16 instructions)
; the current time is P0+88ns (P0 + 10ns + 2 clocks (input synchronizers) + 20 instructions)
set PINS, 0b110 [31] ; enable Data tranceiver & wait until both ~DEVSEL and the written data are valid (P0+210ns)
set PINS, 0b110 [19] ; enable Data tranceiver & wait until both ~DEVSEL and the written data are valid (P0+170ns)
in PINS, 10 ; read R/W, ~DEVSEL, and Data[7:0], then autopush
wait 0 GPIO, PHI0_GPIO [7] ; wait for PHI0 to fall
jmp next_bus_cycle
@ -41,7 +41,7 @@ write_cycle:
read_cycle:
; the current time is P0+82ns (P0 + 10ns + 2 clocks (input synchronizers) + 16 instructions)
set PINS, 0b110 [4] ; ensure AddrLo transceiver is disabled and delay for ~DEVSEL to become valid (P0+102ns+buffer delay)
set PINS, 0b110 [5] ; ensure AddrLo transceiver is disabled and delay for ~DEVSEL to become valid (P0+102ns+buffer delay)
in PINS, 10 ; read R/W, ~DEVSEL, and dontcare[7:0], then autopush
irq set READ_DATA_TRIGGER_IRQ ; trigger the data read state machine to put data on the data bus
@ -66,26 +66,26 @@ wait_loop:
wait 1 irq READ_DATA_TRIGGER_IRQ ; wait for the data portion of a read cycle (from the main SM)
jmp PIN, wait_loop ; skip if this device is not being addressed
; the current time is P0+114ns (P0 + 10ns + 2 clocks (input synchronizers) + 24 instructions) and
; the current time is P0+130ns and
; this read cycle is addressed to this device.
;
; Phase 0 is typically 489 ns long.
; * Data from peripherals should be valid on the data bus by 45 nanoseconds before the end of phase 0
; * Data should be held for 40ns after phase 0 ends
; * Data bus should be tri-stated within 60ns after phase 0 ends
; * Data should be held for no more than 20ns after phase 0 ends
; * Data bus should be tri-stated within 30ns after phase 0 ends
irq set DATA_BUSY_IRQ
set PINS, 0b01 [10] ; enable Data tranceiver with output direction [160ns]
mov OSR, ~NULL [31] ; [288ns]
out PINDIRS, 8 [31] ; set data pins as outputs [416ns]
set PINS, 0b01 [7] ; enable Data tranceiver with output direction [P0+162ns]
mov OSR, ~NULL [31] ; [P0+290ns]
out PINDIRS, 8 [31] ; set data pins as outputs [P0+418ns]
pull noblock ; pull value from the FIFO as late as possible [420ns]
out PINS, 8 ; [424ns]
pull noblock ; pull value from the FIFO as late as possible [P0+422ns]
out PINS, 8 ; [P0+426ns]
; the current time is P0+424ns (P0 + 10ns + 2 clocks (input synchronizers) + 101 instructions)
; the current time is P0+426ns
wait 0 GPIO, PHI0_GPIO [7] ; wait for PHI0 to fall then hold for 40ns (2 clocks (input synchronizers) + 7 instructions)
wait 0 GPIO, PHI0_GPIO [2] ; wait for PHI0 to fall then hold for 12ns (2 clocks (input synchronizers) + 7 instructions)
set PINS, 0b10 ; disable Data tranceiver to tri-state the data bus
mov OSR, NULL