Read/Write to mapped IO

OSByte call Action Available on:
(dec) (hex) BBC Master Electron
146 92 Read IO in &FCxx FRED x x x
147 93 Write IO in &FCxx FRED x x x
148 94 Read IO in &FDxx JIM x x x
149 95 Write IO in &FDxx JIM x x x
150 96 Read IO in &FExx SHEILA x x x
151 97 Write IO in &FExx SHEILA x x x

Entry parameters

X Address within specified page for the call

On exit:

A preserved
X undefined
C undefined

Refer to the hardware secion about the FRED, JIM & SHEILA 1MHz buses.