GN_Rbe, read byte at extended address

RST 20H, DEFW $3E09

IN:

     BHL = pointer to the byte to read (B = 0, local byte)

     A = byte at address

     .FBCDEHL/IXIY same
     A......./.... different

Bugs:
 

Related calls:

GN_Cme, compare null-terminated strings, one local, one extended
GN_Wbe, write byte at extended address
OS_Bde, copy bytes to extended address
OS_Bhl, copy bytes from extended address