Post #1647243
2026-04-03 17:06 UTC
A quick side note: The #Psion SIBO Serial Protocol (SIBO-SP) is a proprietary two-wire serial protocol, a bit like I2C with CLK and DATA lines, and the concept of master and slave devices. (From memory, the term "master" is never used in the HDK, but "slave" is.)
To talk to a slave, the master sends a control frame with an selection ID. For this discussion, all you need to know is ID:2 is ASIC5 and ID:6 is ASIC4.
So, the SIBO-SP control frame "Select ID:6" means, "Hello, are you an ASIC4?" If yes, the response will be a byte with information about how ASIC4 is set up. If no, the response will be 0x00.
(Side-side note: ID:2 is specifically ASIC5 in storage mode. ASIC5 also uses ID:3 for peripherals such as RS232 comms.)
Replies (1)
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@thelastpsion@oldbytes.space 2026-04-03 17:16
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.