Difference between revisions of "CHA256"

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(speculation on how the C-rom jumpers work)
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A [[NEO-273]] and a LS74 are used to address C ROM. The LS74 provides the 2 most significant bits. The LS139 enables one of four pairs of C ROMs using 2 address inputs depending on which 2 jumpers are connected.
+
{| class="wikitable"
 +
|-
 +
!C1/2 ROM type
 +
!Jumper set
 +
|-
 +
|<4MiB
 +
|J15
 +
|-
 +
|4MiB
 +
|J11
 +
|}
  
*Max 256Mbit C ROM (8x 32Mbit)
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{| class="wikitable"
*[[NEO-273]]
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|-
*[[NEO-ZMC]]
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!C3/4 ROM type
*LS139,LS74
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!Jumper set
 +
|-
 +
|<4MiB
 +
|J16
 +
|-
 +
|4MiB
 +
|J12
 +
|}
  
==AES version==
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{| class="wikitable"
 +
|-
 +
!C5/6 ROM type
 +
!Jumper set
 +
|-
 +
|<4MiB
 +
|J17
 +
|-
 +
|4MiB
 +
|J13
 +
|}
  
 
{| class="wikitable"
 
{| class="wikitable"
 
|-
 
|-
!C ROM type
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!C7/8 ROM type
 
!Jumper set
 
!Jumper set
 
|-
 
|-
 
|<4MiB
 
|<4MiB
|J15+J16+J17+J18
+
|J18
 
|-
 
|-
 
|4MiB
 
|4MiB
|J11+J12+J13+J14
+
|J14
 
|}
 
|}
  
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|J2+J3
 
|J2+J3
 
|}
 
|}
 +
 +
A [[NEO-273]] and a LS74 are used to address C ROM. The LS74 provides the 2 most significant bits. The LS139 enables one of four pairs of C ROMs using 2 address inputs depending on which 2 jumpers are connected.
 +
 +
*Max 256Mbit C ROM (8x 32Mbit)
 +
*[[NEO-273]]
 +
*[[NEO-ZMC]]
 +
*LS139,LS74
 +
 +
==AES version==
  
 
{| class="wikitable"
 
{| class="wikitable"

Revision as of 20:23, 13 April 2021

Cha256 mvs.jpg

C ROMs

Up to 8 * 32Mbit ROMs (27C322) can be used for a maximum of 256Mbit. 27C800/27C160 can also be used depending on jumper configuration.

The size of largest ROM is selected using a pair of jumpers. The rest should be left unconnected.

Largest C ROM Jumper set
1MiB J5+J6
2MiB J7+J8
4MiB J9+J10
C1/2 ROM type Jumper set
<4MiB J15
4MiB J11
C3/4 ROM type Jumper set
<4MiB J16
4MiB J12
C5/6 ROM type Jumper set
<4MiB J17
4MiB J13
C7/8 ROM type Jumper set
<4MiB J18
4MiB J14
M1 ROM size Jumper set
64KiB J1+J4
128KiB J2+J3

A NEO-273 and a LS74 are used to address C ROM. The LS74 provides the 2 most significant bits. The LS139 enables one of four pairs of C ROMs using 2 address inputs depending on which 2 jumpers are connected.

AES version

EVEN delay Jumper set
1 gate J19
2 gates J20