From 515fc54f57d2b33da1929cb14b54fc89db41b7aa Mon Sep 17 00:00:00 2001 From: AJR Date: Sun, 28 Jan 2018 13:19:53 -0500 Subject: [PATCH] 74157.cpp: Update notes (nw) --- src/devices/machine/74157.cpp | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/src/devices/machine/74157.cpp b/src/devices/machine/74157.cpp index 6321e9c88dd..8ca2cae3617 100644 --- a/src/devices/machine/74157.cpp +++ b/src/devices/machine/74157.cpp @@ -5,11 +5,19 @@ 74LS157/74HCT157 Quad 2 to 1-Line Data Selectors/Multiplexers (TTL) - Often used to help feed 8-bit ROM data into a MSM5205, and for many - other purposes. + Often used to help feed 8-bit ROM data into a MSM5205 (which may + require additional pullups for CMOS compatibility), and for many other + purposes. 74LS158 has inverted outputs; 74LS157 is non-inverting. + 74LS257 and 74LS258 have three-state outputs with an active-low enable, + making these devices popular for bus-compatible applications which the + emulation here is not particularly suitable for. When pin 15 is tied to + GND, however, these devices become pin-compatible replacements for + 74LS157 and 74LS158; this substitution is somewhat common on arcade + bootlegs. + ***************************************************************************/ #include "emu.h"