From 2e416563f4725348c8508d4fd16a4811ce1a2ab5 Mon Sep 17 00:00:00 2001 From: fulivi Date: Fri, 27 Jan 2017 11:43:58 +0100 Subject: [PATCH] hp9845: some info added for 9895 --- src/devices/bus/ieee488/hp9895.cpp | 36 ++++++++++++++++++++++++++++-- 1 file changed, 34 insertions(+), 2 deletions(-) diff --git a/src/devices/bus/ieee488/hp9895.cpp b/src/devices/bus/ieee488/hp9895.cpp index 8595c654af2..30df3426ac1 100644 --- a/src/devices/bus/ieee488/hp9895.cpp +++ b/src/devices/bus/ieee488/hp9895.cpp @@ -2,12 +2,44 @@ // copyright-holders: F. Ulivi /********************************************************************* - hp9895.cpp + hp9895.cpp - HP9895 floppy disk drive + HP9895 floppy disk drive Phew, this one was tough! + This is a dual 8" floppy disk drive that interfaces through + HPIB/IEEE-488 bus. It implements the so-called "Amigo" command + set. + + Its main components are: + * A Z80A CPU @ 4 MHz with 8 kB of firmware ROM and 1 kB of + static RAM + * A HP PHI chip that interfaces CPU to HPIB bus + * A disk controller implemented with a lot of discrete TTLs + * 2 MPI 8" disk drives + + Data I/O with the disk is carried out through 2 shift registers, + one for data bits (@ 0x60 address) and one for clock bits (@ 0x61 + address). CPU is stalled by setting WAIT/ to 0 whenever it accesses + the data register and the hw is not ready for the byte. Once + the next byte boundary is reached (the SDOK signal activates) the + CPU is released and either the data byte is read from shift register + or written into it. At the same time clock shift register is + copied into clock register when reading or viceversa when writing. + + The 9895 drive can operate in 2 modes: HP/High density or IBM/low + density. This table summarizes the differences between the modes. + See also page 2-12 of service manual. + + | Characteristic | HP mode | IBM mode | + |----------------+----------+-----------| + | Bit cell size | 2 µs | 4 µs | + | Modulation | MMFM | FM | + | Bit order | LS first | MS first | + | Sync bytes | 4x FF | 6x 00 | + | Formatted size | 1155 kB | 250.25 kB | + Reference manual: HP 09895-90030, feb 81, 9895A Flexible Disc Memory Service Manual