diff options
Diffstat (limited to 'src/emu/machine/eeprompar.c')
-rw-r--r-- | src/emu/machine/eeprompar.c | 57 |
1 files changed, 28 insertions, 29 deletions
diff --git a/src/emu/machine/eeprompar.c b/src/emu/machine/eeprompar.c index b4417613c6d..0d730224df3 100644 --- a/src/emu/machine/eeprompar.c +++ b/src/emu/machine/eeprompar.c @@ -37,33 +37,33 @@ **************************************************************************** - Parallel EEPROMs are generally simpler than serial EEPROMs, though - they require more pins to provide the full set of address and data - lines necessary. They also require more pins the larger the EEPROM - is, whereas serial EEPROMs all share the same pinout regardless of - size. - - At a basic level, there are 5 sets of signals involved: - - * /CE = chip enable - * /OE = output enable - * /WE = write enable - * D0-Dn = data lines - * A0-An = address lines - - To access the chip, the various enable states must be asserted or - cleared. Note that these are generally active-low, so asserted means - pulled to GND, and cleared means pulled to Vcc: - - /CE /OE /WE Action - ASSERT ASSERT CLEAR Read (D0-Dn contain output data) - ASSERT CLEAR ASSERT Write/Erase (D0-Dn are input data) - - Erase is performed by doing a write with D0-Dn all set to 1. - - In general, it is slow to write or erase (9ms is quoted in the 2816A - datasheet, for example), and the /WE must be held low for the entire - write/erase duration in order to guarantee the data is written. + Parallel EEPROMs are generally simpler than serial EEPROMs, though + they require more pins to provide the full set of address and data + lines necessary. They also require more pins the larger the EEPROM + is, whereas serial EEPROMs all share the same pinout regardless of + size. + + At a basic level, there are 5 sets of signals involved: + + * /CE = chip enable + * /OE = output enable + * /WE = write enable + * D0-Dn = data lines + * A0-An = address lines + + To access the chip, the various enable states must be asserted or + cleared. Note that these are generally active-low, so asserted means + pulled to GND, and cleared means pulled to Vcc: + + /CE /OE /WE Action + ASSERT ASSERT CLEAR Read (D0-Dn contain output data) + ASSERT CLEAR ASSERT Write/Erase (D0-Dn are input data) + + Erase is performed by doing a write with D0-Dn all set to 1. + + In general, it is slow to write or erase (9ms is quoted in the 2816A + datasheet, for example), and the /WE must be held low for the entire + write/erase duration in order to guarantee the data is written. ***************************************************************************/ @@ -150,8 +150,7 @@ eeprom_parallel_##_lowercase##_device::eeprom_parallel_##_lowercase##_device(con { \ static_set_size(*this, _cells, _bits); \ }; \ -const device_type EEPROM_PARALLEL_##_uppercase = &device_creator<eeprom_parallel_##_lowercase##_device>; \ - +const device_type EEPROM_PARALLEL_##_uppercase = &device_creator<eeprom_parallel_##_lowercase##_device>; // standard 28XX class of 8-bit EEPROMs DEFINE_PARALLEL_EEPROM_DEVICE(28xx, 2804, 2804, 8, 512) DEFINE_PARALLEL_EEPROM_DEVICE(28xx, 2816, 2816, 8, 2048) |