2-20 Service Guide
Table 2-3 M1523 Signal Descriptions (continued)
Signal Pin Type Description
ISA Interface
SA[16:0] 181, 185, 187,
188, 190, 192,
193, 195, 197,
199, 201, 203,
205, 207, 3, 4,
5
I/O ISA Slot Address Bus. These lines are addresses
connected to slot address.
SBHEJ 6I/O ISA Slot Byte-high Enable. In a CPU or PCI master cycle,
this signal is generated by BE3J-BE0J and the chip’s
internal control circuit. In a DMA cycle, it is generated by
internal 8237. In a refresh cycle, it is generated by the
internal refresh circuits. It is an input signal for ISA
master cycle.
LA[23:17] 8, 10, 12, 18,
19, 21, 23 I/O ISA Latched Address Bus. They are input during ISA
master cycle.
IO16J 9IISA 16-bit I/O Device Indicator. This signal indicates the
I/O device supports 16-bit transfers.
M16J 7I/O ISA 16-bit Memory Device Indicator. This signal indicates
the memory device supports 16-bit transfers.
MEMRJ 24 I/O ISA Memory Read. This signal is an input during ISA
master cycle.
MEMWJ 27 I/O ISA Memory Write. This signal is an input during ISA
master cycle.
AEN 173 OISA I/O Address Enable. Active high signal during DMA
cycle to prevent I/O device from misinterpreting the DMA
cycle as valid I/O cycle.
IOCHRDY 172 I/O ISA System Ready. This signal is an output during
ISA/DMA master cycle.
NOWSJ 169 IISA Zero-wait State for Input. This signal terminates the
CPU to ISA command instantly.
IOCHKJ 160 IISA Parity Error. M1523 generates NMI to CPU when this
signal is asserted.
SYSCLK 183 OISA System Clock. This signal provides clocking function
to ISA bus.
BALE 2OBus Address Latch Enable. BALE is active throughout
DMA and ISA master and refresh cycles.
IORJ 180 I/O ISA I/O Read. This signal is an input during ISA master
cycle.
IOWJ 178 I/O ISA I/O Write. This signal is an input during ISA master
cycle.