Post #1647244

2026-04-03 17:16 UTC

ASIC4 and ASIC5 are configured using pull-up and pull-down resistors. These set the number of devices (memory chips), the size of each device (all the same), and a few things like a peripheral ID for certain commercial products (3Link). ASIC5 can address up to 8MB in 4x 2MB banks. The #Psion SIBO Hardware Development Kit docs calls each chip a "device", even though it refers to CS0-CS3 (chip select). ASIC4 is a bit more complicated.

Replies (1)

@thelastpsion@oldbytes.space 2026-04-03 17:25

ASIC4 can work in three different modes: Pack (storage) mode: This is completely compatible with a normal ASIC5, so that it works with older SIBO devices like the MC range and the original Series 3. Accessed with ID:2, just like a normal ASIC5.Extended SSD mode: Can (or not? see the next post) address up to 4x 256MB memory devices. Accessed with ID:6, plus a pull-down on the Mode bit (M=0).Extended Mixed mode: Same as Extended SSD mode, but moves the storage to CS4-CS7 and also adds an extra 4 "peripheral" (IO) devices at CS0-CS4. Accessed with ID:6, plus a pull-up on the Mode bit (M=1). The description of this in the #Psion SIBO HDK is a little confusing. Maybe it's just me, but I've read this paragraph regularly over the course of 8 years and it's only today that I think I've got a grasp of what it actually means. However, the HDK misses one vital piece of information.

Open ##1647245