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READ ENABLE — When RAMCard RAM is read-enabled, sta-
tus bit 1 will be high. When Apple on-board ROM is enabled,
status bit I will be low. This state applies immediately following
power on. When RAMCard RAM is read-enabled, an INH signal
generated by the ICs in sockets U12 and U13 disable the ROMs
on the Apple motherboard.
WRITE ENABLE — When RAMCard RAM is write-enabled,
status bit 2 will be high. The state applies immediately following
power on. When RAMCard RAM is write-protected, status bit 2
will be low. NOTE: Write-enable remains on until a write-pro-
tect control address is accessed. Therefore, accesses to a write-
enable control address subsequent to a write-enable will write to
RAMCard RAM unless a write-protect access intervenes. This
state applies immediately following power on.
NEXT — To protect RAMCard RAM from accidental write-
enable, two consecutive accesses to a write-enable control ad-
dress are required. When the first access has been done, the
NEXT flag is set, and status bit 3 is high. When the second access
has been done and RAMCard RAM is write-enabled, the NEXT
flag is turned off, and status bit 3 is low.
LED Indicators
Three LED indicators are attached to RAMCard along the top edge.
Next to each LED is a label which describes the functions that the LEDs
signal. The three labels are BANK 1, RAM READ ENA, and
RAM WRITE ENA. The LEDs indicate whether the bank or function
is on (selected) or off (deselected), but not whether an access is occur-
ring or not. The LEDs indicate the following:
LED ON OFF
BANK I 4K BANK 1 4K BANK 2
selected selected
RAM READ ENA RAMCard RAM Apple II ROM
read selected selected
RAM WRITE ENA RAMCard RAM RAMCard RAM
write-enabled write-protected
The LEDs may be on or off in any combination because the banks and
functions may be selected in any combination. At power-on/RESET,
RAM WRITE ENA LED is on; the other two LEDs are off.
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